Get rid most of warnings in testing

[menshikh-iv]

Little cleanup for gensim:

• pin pattern version for document building (they make a release after 5 years of silence and new release have breaking dependence like mysqlclient, see https://pypi.org/project/Pattern/#history)
• fix benchmark information in CHANGELOG.md
• get rid almost all warnings from gensim (most of it are DeprecationWarning).

This PR reduced the # of warnings than happens in the test process (python2, linux) from 3550 to 23 (now CI log are readable ⭐ )

[piskvorky]

Nice! Out of curiosity, what are the remaining 23 warnings about?

[menshikh-iv]

@piskvorky

/home/travis/build/RaRe-Technologies/gensim/.tox/py27-linux/lib/python2.7/site-packages/numpy/lib/utils.py:99: DeprecationWarning: `scipy.sparse.sparsetools` is deprecated!
scipy.sparse.sparsetools is a private module for scipy.sparse, and should not be used.
  warnings.warn(depdoc, DeprecationWarning)
/home/travis/build/RaRe-Technologies/gensim/gensim/test/test_doc2vec.py:629: DeprecationWarning: Call to deprecated `syn0_lockf` (Attribute will be removed in 4.0.0, use self.trainables.vectors_lockf instead).
  self.assertTrue(hasattr(model, 'syn0_lockf'))
/home/travis/build/RaRe-Technologies/gensim/gensim/test/test_doc2vec.py:629: DeprecationWarning: Call to deprecated `syn0_lockf` (Attribute will be removed in 4.0.0, use self.trainables.vectors_lockf instead).
  self.assertTrue(hasattr(model, 'syn0_lockf'))
/home/travis/build/RaRe-Technologies/gensim/gensim/test/test_doc2vec.py:629: DeprecationWarning: Call to deprecated `syn0_lockf` (Attribute will be removed in 4.0.0, use self.trainables.vectors_lockf instead).
  self.assertTrue(hasattr(model, 'syn0_lockf'))
/home/travis/build/RaRe-Technologies/gensim/gensim/test/test_doc2vec.py:629: DeprecationWarning: Call to deprecated `syn0_lockf` (Attribute will be removed in 4.0.0, use self.trainables.vectors_lockf instead).
  self.assertTrue(hasattr(model, 'syn0_lockf'))
/home/travis/build/RaRe-Technologies/gensim/gensim/test/test_keras_integration.py:62: UserWarning: Update your `Model` call to the Keras 2 API: `Model(outputs=Tensor("do..., inputs=[<tf.Tenso...)`
  model = Model(input=[input_a, input_b], output=similarity)
/home/travis/build/RaRe-Technologies/gensim/gensim/models/ldaseqmodel.py:290: RuntimeWarning: divide by zero encountered in double_scalars
  convergence = np.fabs((bound - old_bound) / old_bound)
/home/travis/build/RaRe-Technologies/gensim/gensim/interfaces.py:90: UserWarning: corpus.save() stores only the (tiny) iteration object in memory; to serialize the actual corpus content, use e.g. MmCorpus.serialize(corpus)
  "corpus.save() stores only the (tiny) iteration object in memory; "
/home/travis/build/RaRe-Technologies/gensim/gensim/models/phrases.py:598: UserWarning: For a faster implementation, use the gensim.models.phrases.Phraser class
  warnings.warn("For a faster implementation, use the gensim.models.phrases.Phraser class")
/home/travis/build/RaRe-Technologies/gensim/gensim/test/test_similarities.py:605: DeprecationWarning: Call to deprecated `wv` (Attribute will be removed in 4.0.0, use self instead).
  approx_neighbors = model.wv.most_similar([vector], topn=5, indexer=index)
/home/travis/build/RaRe-Technologies/gensim/gensim/test/test_similarities.py:606: DeprecationWarning: Call to deprecated `wv` (Attribute will be removed in 4.0.0, use self instead).
  exact_neighbors = model.wv.most_similar(positive=[vector], topn=5)
/home/travis/build/RaRe-Technologies/gensim/gensim/test/test_word2vec.py:848: DeprecationWarning: Call to deprecated `syn0_lockf` (Attribute will be removed in 4.0.0, use self.trainables.vectors_lockf instead).
  self.assertTrue(hasattr(model, 'syn0_lockf'))
/home/travis/build/RaRe-Technologies/gensim/gensim/models/word2vec.py:1235: DeprecationWarning: Call to deprecated `_minimize_model` (Method will be removed in 4.0.0, keep just_word_vectors = model.wv to retain just the KeyedVectors instance).
  self._minimize_model()
/home/travis/build/RaRe-Technologies/gensim/gensim/test/test_word2vec.py:847: DeprecationWarning: Call to deprecated `syn1neg` (Attribute will be removed in 4.0.0, use self.trainables.syn1neg instead).
  self.assertTrue(hasattr(model, 'syn1neg'))
/home/travis/build/RaRe-Technologies/gensim/gensim/test/test_word2vec.py:848: DeprecationWarning: Call to deprecated `syn0_lockf` (Attribute will be removed in 4.0.0, use self.trainables.vectors_lockf instead).
  self.assertTrue(hasattr(model, 'syn0_lockf'))
/home/travis/build/RaRe-Technologies/gensim/gensim/models/word2vec.py:1235: DeprecationWarning: Call to deprecated `_minimize_model` (Method will be removed in 4.0.0, keep just_word_vectors = model.wv to retain just the KeyedVectors instance).
  self._minimize_model()
/home/travis/build/RaRe-Technologies/gensim/gensim/test/test_word2vec.py:848: DeprecationWarning: Call to deprecated `syn0_lockf` (Attribute will be removed in 4.0.0, use self.trainables.vectors_lockf instead).
  self.assertTrue(hasattr(model, 'syn0_lockf'))
/home/travis/build/RaRe-Technologies/gensim/gensim/models/word2vec.py:1235: DeprecationWarning: Call to deprecated `_minimize_model` (Method will be removed in 4.0.0, keep just_word_vectors = model.wv to retain just the KeyedVectors instance).
  self._minimize_model()
/home/travis/build/RaRe-Technologies/gensim/gensim/test/test_word2vec.py:847: DeprecationWarning: Call to deprecated `syn1neg` (Attribute will be removed in 4.0.0, use self.trainables.syn1neg instead).
  self.assertTrue(hasattr(model, 'syn1neg'))
/home/travis/build/RaRe-Technologies/gensim/gensim/test/test_word2vec.py:848: DeprecationWarning: Call to deprecated `syn0_lockf` (Attribute will be removed in 4.0.0, use self.trainables.vectors_lockf instead).
  self.assertTrue(hasattr(model, 'syn0_lockf'))
/home/travis/build/RaRe-Technologies/gensim/gensim/models/word2vec.py:1235: DeprecationWarning: Call to deprecated `_minimize_model` (Method will be removed in 4.0.0, keep just_word_vectors = model.wv to retain just the KeyedVectors instance).
  self._minimize_model()
/home/travis/build/RaRe-Technologies/gensim/gensim/models/word2vec.py:1235: DeprecationWarning: Call to deprecated `_minimize_model` (Method will be removed in 4.0.0, keep just_word_vectors = model.wv to retain just the KeyedVectors instance).
  self._minimize_model()
/home/travis/build/RaRe-Technologies/gensim/gensim/models/word2vec.py:1140: UserWarning: All the input context words are out-of-vocabulary for the current model.
  warnings.warn("All the input context words are out-of-vocabulary for the current model.")