Mobile Responsiveness Improvements - Bug 903529

Fixes for:
* instructions for bookmarklet install need to be different.
* index page could make better use of space on tablet.
* toolbar shows all options. we might want more functionality exposed in the toolbar for touch, but some (report bug) can stay hidden.
* remix dialog's preview scrolling effect is glitchy, at least on my simulator.
* zooming in on dialogs breaks things.