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ARROW-710: [Python] Read/write with file-like Python objects from read_feather/write_feather

cc @jreback

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

Closes #474 from wesm/ARROW-710 and squashes the following commits:

61d7218 [Wes McKinney] Do not close OutputStream in Feather writer. Read and write to file-like Python objects