add CONTRIBUTING.md (addresses #15)
add CONTRIBUTING.md (addresses #15)

firebase/SwiftLint,lyft/SwiftLint,realm/SwiftLint,wfleming/SwiftLint,lyft/SwiftLint,firebase/SwiftLint,realm/SwiftLint,Johnykutty/SwiftLint,firebase/SwiftLint,dictav/SwiftLint,daniel-beard/SwiftLint,wfleming/SwiftLint,dictav/SwiftLint,realm/SwiftLint,victorpimentel/SwiftLint,jeffreybergier/SwiftLint,victorpimentel/SwiftLint,jeffreybergier/SwiftLint,cdillard/SwiftLint,realm/SwiftLint,Johnykutty/SwiftLint,Johnykutty/SwiftLint,firebase/SwiftLint,jeffreybergier/SwiftLint,jeffreybergier/SwiftLint,Johnykutty/SwiftLint,daniel-beard/SwiftLint,lyft/SwiftLint,cdillard/SwiftLint,victorpimentel/SwiftLint,victorpimentel/SwiftLint,lyft/SwiftLint