[zanata/zanata-server] 4a0497: Add CONTRIBUTING.md

[GitHub]

  Branch: refs/heads/integration/master
  Home:   https://github.com/zanata/zanata-server
  Commit: 4a049705724406423e065c0d2ffc40f70069bd7d
      https://github.com/zanata/zanata-server/commit/4a049705724406423e065c0d2ffc40f70069bd7d
  Author: Sean Flanigan <sflaniga at redhat.com>
  Date:   2015-05-12 (Tue, 12 May 2015)

  Changed paths:
    A CONTRIBUTING.md

  Log Message:
  -----------
  Add CONTRIBUTING.md

See https://github.com/blog/1184-contributing-guidelines for
background.