scaffold of attar change, attach and dettach
now using polymer constructor

encapsulated audio-range element
better lifecycle management
Merge branch 'develop' into feature/onchange
Updated README.md
lifecycle management improvements
two way bindings for options
patch audiocontext multiple instantiation issue in Microphone
patched audiocontext issue in fork of Microphone

In fork, see commit 37140395b125c01d2f32b87032df5ffbcb861014
corrected references to `unit` (should be `length`)
Merge branch 'feature/onchange' into develop