Add travis support on 3.0-stable branch

git-svn-id: http://svn6.assembla.com/svn/pyfits/branches/3.0-stable@2363 ed100bfc-0583-0410-97f2-c26b58777a21
Disable 3.3

git-svn-id: http://svn6.assembla.com/svn/pyfits/branches/3.0-stable@2366 ed100bfc-0583-0410-97f2-c26b58777a21