Added NSDate helper for comparing NSDate objects with common comparison symbols.
Added NSDate helper for comparing NSDate objects with common comparison symbols.

OAuthSwift/OAuthSwift,back2mach/OAuthSwift,back2mach/OAuthSwift,dongri/OAuthSwift,dongri/OAuthSwift,ianbytchek/OAuthSwift,ianbytchek/OAuthSwift,matteobruni/OAuthSwift,matteobruni/OAuthSwift,OAuthSwift/OAuthSwift