Last details on the Workflow

Hide the timeline on startup and show it when we move to the sync
stage.

Have enter create a new subtitle in typing mode.

Only show sync helpers when the timeline is shown.

Make the keybord shortcuts depend on if the timeline is shown, not the
current workflow state.  This way users can manually hide/show the
timeline to get the behavior they want.

Changed CurrentEdit API to not need a LI element.  The controllers
shouldn't be forced to pass that in, and we can easily calculate it
from the directives.
Remove subtitle if the user hits escape with no text.

It's pretty common for me to be in typing mode and hit enter after the
last subtitle that I want to enter.  After I hit escape, I end up with
a blank subtitle, which feels wrong.
Removed unused dependency.
Angular module refactor.

I'm not sure why I thought it was a good idea to have modules like
services, which just import other modules.  We can do that easily from
the app module.

Renamed amara.SubtitleEditor.services.domutil to dom.

Renamed amara.SubtitleEditor.filters to
amara.subtitle.SubtitleEditor.filters.subtitles to match the other
modules.  Removed dependency on the app module, it's not needed at
all.
Moved controllers out of the global scope and into angular modules

This should make them easier to test.
Move DOM-specific code out of WorkingSubtitlesController and into a service

This fixes testing issues.