Improve UI of keyboard shortcuts

[neocotic]

This can be done easily. First, replace the following lines (currently separate) from popup.css:

#templates li > a .pull-right {color: #999;}
#templates li > a:hover .pull-right {color: #FFF;}

With:

#templates li > a .shortcut {font-family: Consolas, "Liberation Mono", Courier, monospace; font-size: 12px;}
#templates li > a:hover .shortcut {color: #FFF;}

And change the following in the buildTemplate function within background.coffee:

  if template.shortcut and store.get 'shortcuts.enabled'
    anchor.append $ '<span/>',
      class: 'pull-right muted shortcut'
      html:  "#{ext.modifiers()}#{template.shortcut}"

This same sort of change should also be applied to the Shortcut column on the Templates tab of the options page.

[neocotic]

This has been implemented as part of #213.