arrow

ARROW-280: [C++] Refactor IPC / memory map IO to use common arrow_io interfaces. Create arrow_ipc leaf library

Several things here

* Clean up IO interface class structure to be able to indicate precise characteristics of an implementation
* Make the IPC reader/writer use more generic interfaces -- writing only needs an output stream, reading only needs a random access reader. This will unblock ARROW-267
* Create a separate arrow_ipc shared library

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

Closes #138 from wesm/ARROW-280 and squashes the following commits:

6a59eb6 [Wes McKinney] * Restructure IO interfaces to accommodate more configurations. * Refactor memory mapped IO interfaces to be in line with other arrow::io   classes. * Split arrow_ipc into a leaf library * Refactor pyarrow and arrow_parquet to suit. Move BufferReader to   arrow_io. Pyarrow parquet tests currently segfault