add integration test

add an integration test of a simple webapp using the Compass framework. Also provide a build configuration for Travis-CI.
actually run integration test
update JRuby to 1.7.13

Also updates some other dependencies:

  * guava
  * rb-inotify
  * maven-plugin-api

and plugins:

  * gem-maven-plugin
  * maven-plugin-plugin

and require at least maven 2.2.1 to build (which was required implicitly anyway, but lets be clear about it)

close #14