Obey shouldChangeCharactersInRange delegate method.
Add tests. Remove const.
Merge branch 'master' of https://github.com/venmo/VENCalculatorInputView

Conflicts:
	VENCalculatorInputView.xcodeproj/project.pbxproj
	VENCalculatorInputViewSample/Podfile.lock
Fix tests
Remove NSLog
Add EOF newline
Merge pull request #17 from ayanonagon/patch-1

Call shouldChangeCharactersInRange delegate method