Update README to include feature list and link to demo
Add "Couldn't initialise microphone" warning

If no microphone is present/available, it would previously leave the user
staring at a garbled interface with no hint of what the problem is.
Add flashvars / options section to readme
Update demo URL in readme
Demo: Switch to Blob constructor (BlobBuilder is deprecated)

BlobBuilder is deprecated and no longer available in most modern browsers.
The Window.Blob() constructor needs to be used instead.