Rewrite runloop guide autorun FAQs

A rewrite of the autorun FAQs in the Runloop guide.

Fixes #1712 #1713 Partially addresses #1390
I was referring to the click handler as a whole. The handler is attached directly to `a` elements. Ember attaches all its event listeners to `rootElement`  (usually `<body>`) so it is likely that the handler in the example will be run before Ember code is entered because Ember will not see the `click` until it bubbles up to `rootElement`. 

That being said, I don' think it adds anything to the explanation in this section and seems to be a source of confusion. Will remove.