Update build tools to 19.1.0 in the Travis cfg
Update build tools to 19.1 in the Travis cfg

Apparently, the version number is (maybe) 19.1 according to http://dl-ssl.google.com/android/repository/repository-8.xml (and not 19.1.0 as expected).
Merge pull request #128 from ninetwozero/update-build-tools-travis

Update build tools to 19.1.0 in the Travis cfg