allowMultipleCallbacks method

calling annyang.allowMultipleCallbacks(true) will allow to recognize multiple commands in a single sentence
this is useful if you expect user to say many commands in a fast manner
Merge branch 'feature-allow-multiple-callbacks'

Conflicts:
	annyang.js
	annyang.min.js
	sites/facebook.min.js
	sites/geektime.min.js