WIP: Refactor back to stores and more robust get()
WIP: Refactor Computed to Getter

Get rid of idea of having Stores with reference to the state their own
state
Remove jest in favor of karma + jasmine
Switch test runner to Karma + Jasmine for 0.5.0-rc1

Tests are green for 0.5.0-rc1

This major change moves some of the design closer to traditional flux
while eliminating the binding of reactor level computeds in favor of at
runtime evaluated Getters.  The syncing mechanism should now be done at
the changeObserver / UI data binding layer.
Add reactor interface doc
Refactor evaluate/getters to fit new interface

`reactor.get` now can take ad-hoc computed values

For more information see reactor-interface.md
Refactor get/observe mechanisms
Expose evaluate and KeyPath
Remove computed.js (replaced with Getter)
Update README for 0.5.0