test_arrow_nonnullable_table fails with arrow 0.15.0

[tobim]

Test output:

============================= test session starts ==============================
platform linux2 -- Python 2.7.16, pytest-4.6.5, py-1.8.0, pluggy-0.12.0
rootdir: /tmp/nix-build-python2.7-awkward-0.12.6.drv-0/awkward-0.12.6
collected 219 items / 4 skipped / 215 selected

tests/test_arrow.py ...................F.........ss.....s.........       [ 21%]
tests/test_chunked.py ........                                           [ 24%]
tests/test_combine.py .                                                  [ 25%]
tests/test_crosscut.py ..                                                [ 26%]
tests/test_generate.py .....................................             [ 42%]
tests/test_hdf5.py ....                                                  [ 44%]
tests/test_indexed.py ............                                       [ 50%]
tests/test_issues.py ...                                                 [ 51%]
tests/test_jagged.py ..............................................      [ 72%]
tests/test_likenumpy.py .                                                [ 73%]
tests/test_masked.py ........                                            [ 76%]
tests/test_methods.py .                                                  [ 77%]
tests/test_objects.py ...                                                [ 78%]
tests/test_persist.py ..................                                 [ 86%]
tests/test_table.py .....................                                [ 96%]
tests/test_union.py ...                                                  [ 97%]
tests/test_virtual.py .....                                              [100%]

=================================== FAILURES ===================================
______________________ Test.test_arrow_nonnullable_table _______________________

self = <tests.test_arrow.Test testMethod=test_arrow_nonnullable_table>

    def test_arrow_nonnullable_table(self):
        if pyarrow is None:
            pytest.skip("unable to import pyarrow")
        else:
            x = pyarrow.array([1, 2, 3])
            y = pyarrow.array([1.1, 2.2, 3.3])
            table = pyarrow.Table.from_arrays([x], ["x"])
>           table2 = table.add_column(1, pyarrow.column(pyarrow.field("y", y.type, False), numpy.array([1.1, 2.2, 3.3])))
E           AttributeError: 'module' object has no attribute 'column'

tests/test_arrow.py:370: AttributeError
=============================== warnings summary ===============================
tests/test_arrow.py::Test::test_arrow_readparquet
  /tmp/nix-build-python2.7-awkward-0.12.6.drv-0/awkward-0.12.6/awkward/arrow.py:486: FutureWarning: The 'field_by_name' method is deprecated, use 'field' instead
    self.type = schema2type(self.parquetfile.schema.to_arrow_schema())

-- Docs: https://docs.pytest.org/en/latest/warnings.html
========= 1 failed, 215 passed, 7 skipped, 1 warnings in 10.56 seconds =========

The arrow::Column class and accompanying python bindings in pyarrow were removed in apache/arrow@5e201fe.
Relevant PR: apache/arrow#4841

[jpivarski]

Thanks! PR #204.