added first line of PR https://github.com/owncloud/android/pull/219

fixing issue pointed out by dper:
https://github.com/owncloud/android/pull/219#issuecomment-26715595
Merge branch 'develop' of github.com:owncloud/android into setup_md
mention contributor-agreement in SETUP.md
"follow" instead of "obey"
positive description about what app does
Merge pull request #287 from LukeOwncloud/setup_md

Setup.md updated.