Enhance `browser.ready`

[sjelin]

In a world without the WebDriver Control Flow, we're going to need browser.ready to be better:

• Initialize to driver.getSession(), since that will wait for the browser session to start
• Update with the result of the getCapabilities() call call in the ProtractorBrowser constructor.
• Update with the setScriptTimeout() call in runner.createBrowser, instead of overwriting
• Update with the browser_.driver.getCurrentUrl() call in forkNewDriverInstance, and also return the result of newBrowser.get(url) in the subsequent then block