Add Keyboard Shortcuts

[wgranger]

This will help improve accessibility #107, and will also help the overall functionality of the site. Upon initial conversation, keyboard shortcuts can be added in the classifier for:

• Toggle previous marks
• Toggle between navigate/annotate

[beckyrother]

Can I also add:

• Shift-Enter to submit classification / close transcribe box
• Esc to cancel transcribe box

[wgranger]

Nice. Also, is there a way we should indicate these options to users? On the classifier somewhere? I'm afraid it might get lost in something like a tutorial, but don't want it to crowd up too much space.

[beckyrother]

What if we do another item in the toolbar with a fa-keyboard-o icon.
Maybe just list them in a grid the same way as in the subject info?

[beckyrother]

*command/control-enter to submit