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ARROW-434: [Python] Correctly handle Python file objects in Parquet read/write paths

While we'd enabled Python file objects for IPC file reader/writer, they hadn't been enabled in the Parquet read/write paths. For example:

```python
with open(filename, 'wb') as f:
    A.parquet.write_table(arrow_table, f, version="1.0")

data = io.BytesIO(open(filename, 'rb').read())

table_read = pq.read_table(data)
```

There was a separate bug reported in ARROW-434, but that's a Parquet type mapping issue, will be fixed in PARQUET-812.

Author: Wes McKinney <wes.mckinney@twosigma.com>

Closes #247 from wesm/ARROW-434 and squashes the following commits:

c704088 [Wes McKinney] Correctly handle Python file objects in Parquet read/write paths