fixing width by using iOS7 methods boundingRectWithSize
use last commit only for iOS 7.0 and above
support any kind of barbuttonitem : navbar, toolbar, tabbar
Merge branch 'bubble-width' into barbuttonitem
Merge branch 'barbuttonitem' into all-top-bottom

Conflicts:
	ProductTour/CRViewController.m
	ProductTour/ProductTour/CRBubble.h
	ProductTour/ProductTour/CRBubble.m