Revert "setup.py: fix x11 compilation"

This reverts commit 12d6cdb97e75bae3859b374a6f6c27d0904fad71.
Revert "Revert "setup.py: fix x11 compilation""

This reverts commit 77b654363158c21e8492126ec40190d96f626724.
doc: revisions to README.md
Merge branch 'master' of git://github.com/kivy/kivy