Update Syntastic to 3.3.0

Unfortunately, the lead developer didn't tag the release, so we're
forced to point to the hash of the version bump.
Add haml-lint checking via Syntastic

Now that `haml-lint` checking is included in Synastic, enable it.
Remove extra message from update script output

This message was redundant since the following line would display
essentially the same information. The only extra value it provided was
telling you which symbolic ref was being updated, but that doesn't seem
important.

Remove it to keep the script lean.