Allow default behavior to include clicking on sound cloud player buttons embbedded in 3rd party sites.

Modelled the default behaviour on facebook behaviour. Default behaviour will try to detect SoundCloud player buttons and click them, which will capture the url of the audio file. Also added --disable-web-security to browser.py since accessing an iframe on a different domain than the parent domain throws a security exception without this setting. Not sure what the security implications of this are though. Needs some thought before merging.