[zanata/zanata-server] 18438c: docs: add CONTRIBUTING.md

[GitHub]

  Branch: refs/heads/contributing
  Home:   https://github.com/zanata/zanata-server
  Commit: 18438cc47b7789d105358f329beebfe7316ca4a5
      https://github.com/zanata/zanata-server/commit/18438cc47b7789d105358f329beebfe7316ca4a5
  Author: Ding-Yi Chen <dingyichen at gmail.com>
  Date:   2016-03-11 (Fri, 11 Mar 2016)

  Changed paths:
    M CONTRIBUTING.md

  Log Message:
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  docs: add CONTRIBUTING.md