Adds support for services which wrap other services.

First and foremost, thank you for publishing this library and your continual work in improving and supporting it.  My company over the past few months has found it invaluable.

This small modification was required as if one wishes to add bundles, resources, etc. in a generic fashion to a Dropwizard service and is using version 0.6.0 or later, one needs to establish an AOP-style cutpoint on the abstract initialize and run methods.

In previous versions of Dropwizard (namely 0.4.x and 0.5.x), this procedure was a bit more straight forward.

While I realize this may be a somewhat esoteric use case, this patch enables support for this functionality in a way which is completely opaque to users of Dropwizard, and hopefully shouldn't be a maintenance burden.

Cheers,

Brett