Commits
Wes McKinney authored b0e3122b904
ARROW-724: Add How to Contribute section to README Author: Wes McKinney <wes.mckinney@twosigma.com> Closes #504 from wesm/ARROW-724 and squashes the following commits: c1e07b6 [Wes McKinney] Typo 3a6083c [Wes McKinney] Add how to contribute section modifed from parquet-mr