arrow

ARROW-2611: [Python] Fix Python 2 integer serialization

Fixes an issue where serialization turns integers into longs in Python 2.

```python
In [1]: import pyarrow as pa

In [2]: value = 1

In [3]: type(value)
Out[3]: int

In [4]: serialized = pa.serialize(value)

In [5]: deserialized = serialized.deserialize()

In [6]: type(deserialized)
Out[6]: long
```

Author: Peter Schafhalter <pschafhalter@berkeley.edu>

Closes #2055 from pschafhalter/fix-python2-int-serialization and squashes the following commits:

7b96b679 <Peter Schafhalter> Fix bug with Python 3 C++ API
5d8ff268 <Peter Schafhalter> Add type checking in assert_equal
d5e5e5db <Peter Schafhalter> Fix python2 integer serialization bug