Rename `NSString+Parsimmon` to `NSString+VENCalculatorInputView`
Bump podspec to v1.3.1
Merge branch 'master' of https://github.com/venmo/VENCalculatorInputView

Conflicts:
	VENCalculatorInputView.xcodeproj/project.pbxproj
	VENCalculatorInputViewSample/Podfile.lock