Adds a prereleaser hook for zest.releaser to update the VERSION variable in setup.py. This used to work out of the box but we changed it from 'version' to 'VERSION' and now it no longer works.  I need to submit an upstream fix to zest.releaser to make this case-insensitive. This works in the meantime.
Merge branch 'master' of github.com:astropy/astropy
Updated travis.yml to allow build_sphinx command
Commented out much of the travis build temporarily for testing
added code to allow returning the warnings count from build_sphinx
add "-w" to build_sphinx call in travis