Fix for injector warning when chaining together commands

The warning is occurring when one command triggers another command via a signal where BOTH commands require injections of the same type. Triggering the second command with a type not injected into the first results in no warning.
The fork contains exactly the solution presented here (which now works fine in my tests):
http://stackoverflow.com/questions/12759831/robotlegs-with-signals-warning-injector-already-has-a-rule-for-type/12767463#12767463