2.1.0: Don't Fall Asleep

Since 2.0.2:

• Swift 2.2 compatibility
• README and documentation improvements (#130, #131, #134, #144, #146)
• Default protocol implementation for toJSON() on RawRepresentable (#139, #140, thanks @AquaGeek!)
• Provide better optional-handling options to JSON subscripting (#148, #149)
• Detect and catch integer overflow (#151, #152)
• Framework build fixes (#155, #156; thanks @fabiomassimo and @mz2!)