Added support for multiple crouton managers
clean up of clearForActivities
Merge branch 'multiple-croutons-pick' of github.com:chrisjenx/Crouton

Conflicts:
	library/src/de/keyboardsurfer/android/widget/crouton/Crouton.java
	library/src/de/keyboardsurfer/android/widget/crouton/Manager.java
	sample/src/de/keyboardsurfer/app/demo/crouton/CroutonFragment.java
fixed merge