Add support for browser extensions code

Browser extension's code (e.g. chrome extensions, opera add-ons, firefox add-ons) is executed in a local sandbox environment and it has specific protocol.
E.g. chrome extension's background page may have URL like this:
chrome-extension://ifglblkjlploneiecogcdgejdnpjemom/_generated_background_page.html

To make it possible to use TraceKit inside an extension (especially in raven.js) we need to add special protocols to URL parser regexp.

Protocols are:
chrome-extension:// for Chrome extensions
chrome:// for Firefox add-ons
widget:// for Opera add-ons

So I just add them as a possible protocol values, like http or https.