Extract request/result classes out of dispatcher module
Slight refactoring of Dispatcher module

No changes to API, just tightens up internal API and adds unit
tests for all functionality
Split messages into seperate modules

Just refactoring no functional changes, tests updated to reflect
new layout and expand on coverage
Update examples & bins to reflect reorg

Small related fixes / tweaks to other rjr modules to shore
things up and keep specs in sync