Prerelease 2018-06-11

This is a slightly different prerelease approach leading up to Rodux 1.0, alongside Roact 1.0.

This release rolls up all of the changes since prerelease 2 a couple months ago:

• Added combineReducers utility, mirroring Redux's (#9)
• Added createReducer utility, similar to redux-create-reducer (#10)
• type is now required as a field on all actions
• Introduced middleware (#13)
  • Thunks are no longer enabled by default, use Rodux.thunkMiddleware to add them back.
  • Added Rodux.loggerMiddleware as a simple debugger
  • The middleware API changed in #29 in a backwards-incompatible way!
    • Middleware now run left-to-right instead of right-to-left!
• Errors thrown in changed event now have correct stack traces (#27)

The next release should hopefully be 1.0!