BLD/TST: add pyarrow on CI to macosx build
xref https://github.com/pandas-dev/pandas/pull/18662#issuecomment-350553687

Currently failing

on pyarrow 0.7.1, fp 0.1.3, on macosx
```
(pandas) bash-3.2$ pytest pandas/tests/io/test_parquet.py --tb=short
=========================================================================================== test session starts ===========================================================================================
platform darwin -- Python 3.6.1, pytest-3.2.1, py-1.4.34, pluggy-0.4.0
rootdir: /Users/jreback/pandas, inifile: setup.cfg
plugins: xdist-1.16.0, cov-2.3.1
collected 38 items                                                                                                                                                                                         

pandas/tests/io/test_parquet.py .....F............s...s...x...s.s.....

================================================================================================ FAILURES =================================================================================================
_________________________________________________________________________________________ test_cross_engine_pa_fp _________________________________________________________________________________________
../miniconda3/envs/pandas/lib/python3.6/site-packages/fastparquet/api.py:96: in __init__
    with open_with(fn2, 'rb') as f:
../miniconda3/envs/pandas/lib/python3.6/site-packages/fastparquet/util.py:44: in default_open
    return open(f, mode)
E   NotADirectoryError: [Errno 20] Not a directory: '/var/folders/h3/mr_r3bkj5yg0pbx9fr3tk1r00000gp/T/tmpii71wdx8/_metadata'

During handling of the above exception, another exception occurred:
../miniconda3/envs/pandas/lib/python3.6/site-packages/fastparquet/api.py:119: in _parse_header
    fmd = read_thrift(f, parquet_thrift.FileMetaData)
../miniconda3/envs/pandas/lib/python3.6/site-packages/fastparquet/thrift_structures.py:22: in read_thrift
    obj.read(pin)
../miniconda3/envs/pandas/lib/python3.6/site-packages/fastparquet/parquet_thrift/parquet/ttypes.py:1899: in read
    _elem53.read(iprot)
../miniconda3/envs/pandas/lib/python3.6/site-packages/fastparquet/parquet_thrift/parquet/ttypes.py:1742: in read
    _elem33.read(iprot)
../miniconda3/envs/pandas/lib/python3.6/site-packages/fastparquet/parquet_thrift/parquet/ttypes.py:1656: in read
    self.meta_data.read(iprot)
../miniconda3/envs/pandas/lib/python3.6/site-packages/fastparquet/parquet_thrift/parquet/ttypes.py:1487: in read
    self.statistics.read(iprot)
../miniconda3/envs/pandas/lib/python3.6/site-packages/fastparquet/parquet_thrift/parquet/ttypes.py:298: in read
    iprot.skip(ftype)
../miniconda3/envs/pandas/lib/python3.6/site-packages/thrift/protocol/TProtocol.py:208: in skip
    self.readString()
../miniconda3/envs/pandas/lib/python3.6/site-packages/thrift/protocol/TProtocol.py:184: in readString
    return binary_to_str(self.readBinary())
../miniconda3/envs/pandas/lib/python3.6/site-packages/thrift/compat.py:37: in binary_to_str
    return bin_val.decode('utf8')
E   UnicodeDecodeError: 'utf-8' codec can't decode byte 0xb5 in position 2: invalid start byte

During handling of the above exception, another exception occurred:
pandas/tests/io/test_parquet.py:186: in test_cross_engine_pa_fp
    result = read_parquet(path, engine=fp)
pandas/io/parquet.py:211: in read_parquet
    return impl.read(path, columns=columns, **kwargs)
pandas/io/parquet.py:123: in read
    return self.api.ParquetFile(path).to_pandas(columns=columns, **kwargs)
../miniconda3/envs/pandas/lib/python3.6/site-packages/fastparquet/api.py:102: in __init__
    self._parse_header(f, verify)
../miniconda3/envs/pandas/lib/python3.6/site-packages/fastparquet/api.py:122: in _parse_header
    self.fn)
E   fastparquet.util.ParquetException: Metadata parse failed: /var/folders/h3/mr_r3bkj5yg0pbx9fr3tk1r00000gp/T/tmpii71wdx8
======================================================================== 1 failed, 32 passed, 4 skipped, 1 xfailed in 2.93 seconds ========================================================================
```