Fragment handling for hash bang URLs

I just pushed a fix to fragment handling for hash bang URLs : 45becbc28e217066cabf6331fc61fa1abad95b9f

Basically two things were broken:
- the override to Backbone.history.saveLocation()
- getFragment() stripped out the `!` leading to mismatches of same URLs in `checkUrl()` (`!/path` != `/path`)

The fix brings extensive overrides to backbone which I'd rather avoid. The messiness stems from the fact that with hash bang (`#!`) URLs what's in the browser history (`!/path`) is different from the actual routes (`/path`) and thus non-JS fallbacks (`http://example.com/path`).