Bug 1034600 - [Messages] Suggestions list is badly located. r=julien

* Recipient suggestions container moved to more appropriate place;
* Recipient suggestions now occupy all possible space minus heights of the app header and message "To" field.
* ```.contact-list``` styles are cleaned up a bit.
in current code, we create this `<ul>` on the fly especially because we share the space with the main container. Now that we have a specific component for this, how about creating the `<ul>` in the markup and attach the event handlers in `init`?