Enable puppet-lint in Travis checks

.travis.yml

@@ -4,7 +4,7 @@ rvm:
   - 1.8.7
   - 1.9.3
   - 2.0.0
-script: "bundle exec rake spec SPEC_OPTS='--format documentation'"
+script: "bundle exec rake spec SPEC_OPTS='--format documentation' && bundle exec rake test"
 branches:
   only:
     master