v1.2.1

• Fix a crash when sending more than 65535 pings (thanks to @Kususumu)
• Overall better handling of sequence indices. All the functions and result structs now use the appropriate integer types. This may be a breaking change if you depend on those values being Int types.
• There's a new trueSequenceNumber in PingResponse and a similar private variable in SwiftyPing, which is now returned by currentCount. trueSequenceNumber is an UInt64, which will probably never overflow. This keeps track of the actual number of pings sent, even when sequenceNumber, which is just an UInt16, has overflowed and been wrapped back to 0.