remove mentions of ijson and khmer (#1140)

* remove mentions of ijson and khmer
* fix deprecated test comment

doc/developer.md

@@ -8,7 +8,7 @@ You can get the latest development master branch with:
 git clone https://github.com/dib-lab/sourmash.git
 ```
 sourmash runs under both Python 2.7.x and Python 3.5+.  The base
-requirements are screed and ijson, together with a Rust environment (for the
+requirements are screed and cffi, together with a Rust environment (for the
 extension code). We suggest using `rustup` to install the Rust environment:
 
     curl https://sh.rustup.rs -sSf | sh

doc/release.md

@@ -113,7 +113,7 @@ deactivate
 source bin/activate
 python -m pip install -U setuptools pip wheel
 # install as much as possible from non-test server!
-python -m pip install screed pytest numpy matplotlib scipy khmer ijson bam2fasta deprecation cffi
+python -m pip install screed pytest numpy matplotlib scipy bam2fasta deprecation cffi
 python -m pip install -i https://test.pypi.org/simple --pre sourmash
 sourmash info  # should print "sourmash version ${new_version}${rc}"
 ```

tests/test_deprecated.py

@@ -2,7 +2,7 @@
 from . import sourmash_tst_utils as utils
 
 def test_load_textmode(track_abundance):
-    # ijson requires a file in binary mode or bytes,
+    # ijson required a file in binary mode or bytes,
     # but we had an API example in the docs using 'rt'.
     # I fixed the docs, but I'm keeping this test here
     # to make sure we still support it =/