docs(guide/$location): fix broken example demo

The demo of the hash-bang vs html5-mode deep links was broken since the introduction
of a check for previously bootstrapped elements. See this commit: 3ee744cc63

We fix this problem by applying a null for the injector value of the element of the
at the root of the sub-app.
It also turns out that it was not necessary, and if fact broke the demo, to replace
the $document service for the sub-app.  This was because the $compile service calls
`$document.createElement()`, which doesn't exist on a `div`.
Finally, the bootstrap CSS was limiting the width of the ngAddress bar input box,
which made it difficult to see the changing URLs.