Make InstantClick work on more sites without configuration

The goal of these changes is to make IC work on more sites without requiring the addition of `data-` attribute configuration.  Before these changes, it was common for sites which had changes in their head to break after IC navigation.  I tried to make the commit messages descriptive, so please consult them for a specific list of the changes required.

Here's a few examples of sites broken w/ master which now work:

- dropbox.com – Click “Mobile” in the footer
- mit.edu – Click “About” or “Visiting"
- twitter.com/privacy – Click “About Us” in the footer
- nytimes.com – Click “Opinion” in the top nav, or worse, click an article title
- apple.com – Click “iPhone"
- github.hubspot.com/offline/docs/welcome – Click “Documentation”

The one note about these changes is they don't target Firefox before version 13.  This amounts to about 0.2% of the web browser market.  If this is an issue, let me know and I will tweak the solutions to work on those older browsers as well.
We now bind these events to the document both for efficiency, and to allow the page's javascript to intercept the call if it needs to.  For example, the ArsTechnica.com site uses js events to open a menu, rather than navigating, when you click an item in the header.  Before this change, IC was acting on the event before the page had a chance to.