Refactored things a bit to work on standard Java/Groovy Gradle projects

I love your plugin, however, it seems rather tied directly to Android based projects. So, I've updated the default Guard file template to watch a standard Java directory structure and made the Guard logic execute single test for Gradle. If the file isn't found then the entire test suite is executed. I also added some simple tests, which required that I add some new dependencies (however, they aren't required for people that use the GEM). 

If you aren't happy w/this Pull Request, maybe we should rename your plugin to Guard:Android and then this PR could become the more generic Guard:Gradle? 

What do you think?