etcd_tools.go is not dependent on the specific implementation
(which is provided by pkg/api). All EtcdHelpers are created
with an encoding object which handles Encode/Decode/DecodeInto.
Additional tests added to verify simple atomic flows.
Begins to break up api singleton pattern.
* Made externalize/internalize generic to prevent boilerplate.
* Add fuzz testing.
* All objects pass fuzz tests now.
* This turned up some things we'll need to fix eventually. Left TODOs.
