Added reactive versions of main Activities/Fragments

Includes both built-in versions + support versions.

Minus any sort of weird annotation hacking, this seems to be the "best" method
for creating a version of the base UI component classes that we can hook into.
Added sample Activity demonstrating LifecycleObservable
Add Rx utilities to ReactiveDialog
Merge pull request #93 from dlew/dlew/reactive-ui

Added reactive versions of Activities and Fragments