Remove dependency on Spring and Groovy

[jean-morissette]

First, congratulations for your project and thanks for your open source contribution!

We have rewritten your test cases in pure Java - just keeping junit dependency - to help us track some corner issues. Please let me know if you are interested by a pull request. Maybe it could help the project since Groovy can be scary for some developpers and not everyone want to add Spring to their stack.

[manuel-mauky]

The spring dependency is only for tests, isn't it?. Developers don't need to "add Spring to their stack" if they only use the library.

For me the groovy tests were a little scary too but not so much that they would have discouraged me from contributing. However, I would feel more familiar with JUnit too.