Update .travis.yml
Update .travis.yml

Remove JDK6 - a bug in compilation of generics that won't be updated in OpenJDK6 is fixed in Oracle and Open JDKs 7.  For now, don't compile with 6.
kidaa/truth,google/truth,hcoles/truth,andyglick/truth0,dahlstrom-g/truth,cgruber/truth,google/truth,hcoles/truth,andyglick/truth0,dahlstrom-g/truth,google/truth,cgruber/truth,kidaa/truth