CI support for Calatrava

This patch introduces Travis CI integration into Calatrava. Here are the build steps:

1. rake test
2. bin/calatrava create sample --dev
3. cd sample
4. bundle install
5. rake bootstrap
6. rake clean precommit:mw
7. rake droid:build ios:build web:build

Upon merging the pull request, please follow the Travis CI [getting started](http://about.travis-ci.org/docs/user/getting-started/).