Firefox v53 fix

• Added support for navigator.mediaDevices.getUserMedia (Fix for Firefox v53)
• Bumped opus version to v1.1.4
• Added Unit tests which are running on CircleCi
  -initStream will now return a Promise as well as publish the event when the stream is ready
• Added example to encode from a file
• Build libopus with NO_DYNAMIC_EXECUTION flag
• Adjusted project file structure.
• Added support for module exports and ASM
• Added config option for encoderComplexity which allows tweaking of libopus computational complexity