Add the ability to remove a specific action or filter callback.
Remove unused variable.
Refactoring of _runHook(). Move the hook type test out of the loop
Fix the in-loop splicing in _removeHook()
_removeHook(): rename variable subscribers to handlers
Rename variable hooks to handlers
Remove handlers by callback or by (callback, context)
Merge pull request #10 from mgiulio/master

Remove hook by callback and _runHook() refactoring