Update broccoli-jshint.

0.5.0 now inherits from broccoli-filter which allows much more efficient
caching between reloads (i.e. only calls JSHint on individual files that
have changed).
Merge pull request #758 from rjackson/update-jshint

Update broccoli-jshint.
Add CHANGELOG entry for #758.
Show detailed rebuild timing information.

Uses the same logging as Broccoli itself. By default it logs any trees
that took greater than 5% of the total build time.

Also, we now print `Built Successfully - XXXms.` for each rebuild to
assist in tracking down performance issues. We may decide to remove the
more verbose logging at a later time once things are better understood
(and we have near constant time rebuilds).