Removed external repositories.

If we want publish in central repository all dependency should be already in central.
Otherwise other people's build might break because of missing dependencies
Removed SLF4J bindings from transitive dependencies.

The code only required SLF4J Api, SLF4J binding is required only during tests.
Other people may want to use another implementation of SLF4J binding in their projects.
Merge pull request #11 from slawekjaranowski/master

External repository and SLF4J bindings