Fix tests
Merge branch 'fix-tests' of github.com:mrmr1993/vimium
Help text for non-empty text options.
Remove "Restore to defaults" button.

And line up main frame with the first two columns of the main options
table.
Move "Custom key mappings" above the fold.
Activate "Save" button on input.
Activate "Save" button on input (non-empty text areas).
Fix browser prefix detection
Force our key event handlers to have the highest possible priority

* The `window` object receives key events before the `document` object,
and so any event listeners on `window` get priority. This commit
switches from binding `keydown`, `keypress`, `keyup` on `document` to
on `window`.
* We were using `event.stopPropagation()` to prevent other event
listeners from firing if we had handled an event. This stopped the event
from propagating to other elements/objects and triggering their event
listeners, but didn't block event listeners registered on the same
object as ours. Switching to `event.stopImmediatePropagation()` ensures
that our event listener is the last to run for the event.

Fixing these issues allows Vimium to regain control over key events in
Google Groups (eg. the [vimium-dev
group](https://groups.google.com/forum/vimium-dev)).
Refactor Utils.hasChromePrefix and add tests.
Merge Utils.hasChromePrefix from mrmr1993.
Optional custom new tab URL

This resolves #979.
Automatically load content scripts into the options and blank pages

Load all appropriate content scripts by traversing the list in the
manifest. This removes the need to list them manually.
Merge pull request #1219 from mrmr1993/fix-google-groups

Force our key event handlers to have the highest possible priority
Centralize handling of event propagation.
Merge branch 'customNewTabPage' of github.com:mrmr1993/vimium into mrmr1993-customNewTabPage
Cosmetic tweaks for @smblott-github
Merge branch 'customNewTabPage' of github.com:mrmr1993/vimium into mrmr1993-customNewTabPage
Touch up options page (newTabUrl).
Don't skip installing listeners.

Fix listener installation bug.  To see bug, do:

   - open vimium options page
   - use 'b' to select and go to a bookmark
   - use <alt-LEFT_ARROW> to return to options page
   - vimium key bindings are now *not* installed

Bug was introduced in 28e9c8374bfc7a4fd479dbb958a4a87331fb0857.