Major Changes

• Python 3 support fixes (#140, #155, #159)
• Generic token-parsing plugins support (#162)
• Generic authentication plugins support (#172)
• Fixed frame corruption on big-endian systems (#161)
• Support heartbeats (via PING) and automatic responses to PONG (#169)
• Automatically reject unmasked client frames by default (strict mode) (#174)
• Automatically restart interrupted select calls (#175)
• Make 'run' respect environment settings (including virtualenv) (#176)