Introducing the activity registry
WIP, creating the appropriate domain on SDB.

Still need to figure out how to mock/stub SDB so we don't need to hit AWS for the tests.
Still pondering when to persist and retrieve the attributes stored in SDB.
Figured out persisting attributes to SDB.

Well... I think. Now I need to figure out how to take them out.
Got the activity task completed handler to work using the registry.
Converted the failed job handler to use the activity registry to
get the instructions on what to do on a failure.
Start testing on 2.0.0
Map is no longer required at runtime.
Sometimes inheritance isn't all that bad...
Making progress....
Adding more tests...
Making sure that the activity runs the block passed to it...
This might just work...
Big enough changes to warrant bumping to 0.3.0