")]}\',\n" is a commonly used security prefix added to json http
responses iat google and elsewhere in order to prevent certain
cross-site attacks

$xhr service now autodetects the prefix and strips it before
deserializing the json.

the implementation should be more flexible to allow for wider range
of prefixes, but we need this one right now and can address other
usecases later.

angular.compile()() returns {scope:scope, view:view},
this isn't useful at all and only makes tests more verbose.
Instead, this change makes the linking function return scope directly
and if anyone needs the linked dom there are two ways to do it
documented in angular.compile.

other changes:
- moved angular.compile docs to the compiler so that they are closer to
  the compiler
- fixed some typos and updated angular.compile docs with the new return
  value

- added a spec for dependency graph resolution
- also simplyfying cache presence check

Closses #112