Simplified the Makefile.

The previous Makefile was somewhat of a playground for experimentation.
This is much simpler/straightforward now.

TBR=neil.fraser@gmail.com

Review URL: https://codereview.appspot.com/7187043

git-svn-id: http://blockly.googlecode.com/svn/trunk@595 c400ca83-b69d-9dd7-9705-49c6b8615e23