Linux bug fix

Fixed a bug where, for some reason (I can find no documentation), the [chrome.runtime](http://developer.chrome.com/extensions/runtime.html) API on linux systems does **not** have the methods required for [message passing](http://developer.chrome.com/extensions/messaging.html) while Windows and OS X do not share this problem.

All relevant method references have been changed to their old (now deprecated) references on the [chrome.extension](http://developer.chrome.com/extensions/extension.html) API for cross-platform compatibility.