Allow open popups from bookmarklets. Fix #968.

Use the `openUrlInCurrentTab` message to open bookmarklets so they are opened
via `chrome.tabs.update` instead of an injected script element. This allows
bookmarklets to open popups.
Move the vomnibar to an iframe
Merge pull request #981 from sharat87/bookmarklet-popups
Hacks to make Vomnibar tests work again