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PARQUET-835: Read Arrow columns in parallel with thread pool

Also implements PARQUET-836, but need to add a unit test for that

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

Closes #222 from wesm/PARQUET-835 and squashes the following commits:

71c700e [Wes McKinney] Add missing include. Update Arrow version
638b4c0 [Wes McKinney] cpplint
7c79ca7 [Wes McKinney] Read Arrow columns in parallel with thread pool

Change-Id: I073f3fa2e49384f706597a343688db04e04843e4