Evolutionary bits ...

- First stab at async repository support (experimental and flawed at
this point)
- Welcome StreamSource (simple event store integration bits, home of a
future memory and a sql-based implementation) the home of the default
repository implementation.
- Ditched the naming support in test specifications (doesn't feel "core"
enough).
- Started testing "Testing" (got my work cut out).
- Realized integration tests are going to be welcome soon
- Ditched TryGet in favor of the more monadic GetOptional (using the new
Optional class (the maybe monad)).