v2.0.1

• add example for mux.middleware #126
• fix docs for mux.middleware #127
• fill path in function (m Message) String()

v2.0.0

• protocols are separated to packages
• observe work's natively (#12, #99)
• support's separate message
• don't propagate reset message to client(#110)
• body as ReadSeeker for easy transfer files
• ability to set source port (#90)
• (un)marshal udp/tcp coap message without allocation
• added support for middleware to mux #73