Async Stub

Async stub spike

Separated AsyncStub to its own file & Add more tests

New AsyncStub implementation

Added support for stubbing multiple types of object

Can stub the same message multiple times

Added test for multiple messages on the same class

The recorded calls should get execute only once

Restore Viki.run after finishing the spec

Polished async stub

1.3.0
Merge branch 'master' into cache-api

Conflicts:
	lib/viki/version.rb