Add popin alignement option and update demo
Merge branch 'feature/alignementOption' of https://github.com/leverdeterre/MaryPopin into leverdeterre-feature/alignementOption
Minor refactoring
Added documentation to new enum value
Merge branch 'leverdeterre-feature/alignementOption' into develop

Conflicts:
	MaryPopin/UIViewController+MaryPopin.h
	MaryPopin/UIViewController+MaryPopin.m
	MaryPopinDemo/MaryPopinDemo/BKTViewController.m
	MaryPopinDemo/MaryPopinDemo/en.lproj/Main_iPhone.storyboard
Fixed animation issue with frame offset
Fixed typo in a method name
Updated demo