Feature/dropwizard bundle

This comprises of 3 changes, all of which I needed to use this library with my dropwizard application.

0. Supporting dropwizard Bundles, which means you can add your own logic & configuration. The change could have been better (such as moving the config to an interface) but would have broken backward compatibility.
0. Extending the SpringConfiguration to allow beans to be created through the configuration.
0. Enabling the methods to be overridden if necessary through unofficial APIs, protection moving from private to package-local making minor extensions much simpler. As the code is single threaded, the risks here are limited.

The README.md has been updated with examples. I've released this into my private repository at 0.7.0 as it was a functional change.