Current TODO list:

1. Finish extensions support [enums, messages, nested, more tests]
2. Unit testing [ongoing]
3. More as.Message methods [have patch, needs cleanup]
4. Replace usage of RCPP_FUNCTION_* macros with Rcpp Modules or Attributes.
5. Clean up formatting / whitespace.
6. Add more documentation / examples.

Older stuff

    o   finalizers [murray: what is needed here?]
    o   http-powered rpc implementation [maybe]
    o   what to do when unload the package
    o   useR abstract [done]
    o   useR presentation [done]
