Protocol Buffer support

Initial work on adding a jersey provider for Protocol Buffers.  @skamille, this is what we were discussing in https://github.com/GeneralElectric/snowizard/issues/7.  I don't think we can automatically register this provider if the module is included, so I'll be sure to include information in the docs on how that is done.  Same with the `InvalidProtocolBufferException` mapper.  I wanted to just submit this for now to get feedback on if this is the correct approach.

Remaining work:
- [ ] documentation
`.type()` may not be required here, but I added for explicitness sake