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.
docs(rootScope): improve grammar and clarity

Closes #4234
docs($sce): fix punctuation

Closes #4235
docs(angular.bind): clarify that bind is partial application

The `angular.bind` function reflects the definition of "partial application", which
reduces a function's arity rather than transforming a function with n args into a
chain of n functions, each having a single arg.

curry : f(x,y,z) -> f(x)(y)(z)
partial application : f(x,y,z) -> f(x)(y,z)

Closes #4239
docs(guide/directive): fix indentation in example code

Closes #4241
docs(guide/directive): clarify use of binding to scopes

The use of 'angular' as sample text is confusing to the newbie in that they are forced
to confirm that the text 'angular' is not a keyword or otherwise referring to a system
component. This is changed to a more obvious sample text.

The most common form of `ngBind` is moved to the top of the list.

Closes #4237