Add validate and lint tasks to travis script

.travis.yml

@@ -1,7 +1,7 @@
 ---
 language: ruby
 bundler_args: --without development
-script: "bundle exec rake spec SPEC_OPTS='--format documentation'"
+script: "bundle exec rake validate && bundle exec rake lint && bundle exec rake spec SPEC_OPTS='--format documentation'"
 matrix:
   fast_finish: true
   include: