[zanata/zanata-common] 5ca0a7: docs: add CONTRIBUTING.md

[GitHub]

  Branch: refs/heads/release
  Home:   https://github.com/zanata/zanata-common
  Commit: 5ca0a7e345b4be7017a585d6635db1dd929eeb08
      https://github.com/zanata/zanata-common/commit/5ca0a7e345b4be7017a585d6635db1dd929eeb08
  Author: Ding-Yi Chen <dingyichen at gmail.com>
  Date:   2016-03-11 (Fri, 11 Mar 2016)

  Changed paths:
    A CONTRIBUTING.md

  Log Message:
  -----------
  docs: add CONTRIBUTING.md