Ported build over to Gradle

Hello! Some of us here at Puppet Labs are using ci-eye for our build radiators and I'd like to start extending its functionality a bit, but before I do that I'd really like to use a modern build system. This PR converts the build to gradle and the following commands will be the ones a person would need for development:

`gradle fatJar` - Build the fat jar and place it in the ./build/lib directory.
`gradle idea` - Generate Idea project files. 
`gradle eclipse` - Generate Eclipse project files.