README.md Improvements

[cmeiklejohn]

The README.md for this project should be improved to include more information about the peer service used in this implementation. While it briefly mentions that it is based on the Riak DT ORSWOT implementation, it should clarify that the original Epidemic Broadcast Trees paper doesn't focus on the implementation of the peer service, and that the peer service implementation in this library is ad-hoc for Helium's use case.

In the interest of full disclosure, this peer service should be noted that it exists only in implementation: it's semantics have not been formally or informally specified or verified.