Make sure to notify the delegate when the callout is dismissed

Signed-off-by: Blake Skinner <bskinner@mit.edu>
Add a new version of the MGSCalloutView. This should be a bit nicer to work with (and have a more predictable layout)

Signed-off-by: Blake Skinner <bskinner@mit.edu>
Use the updated MGSCalloutView

Signed-off-by: Blake Skinner <bskinner@mit.edu>
Merge remote-tracking branch 'origin/3.4-dev' into 3.4/master