Add background
Semi-style header

Include a bunch of fonts to experiment & see what looks best.
Style URL input
Style the '+' URL button
Style keyboard key inputs
Improve key input styles
Improve positioning of edit sample area

* Vertical align middle
* Increase height of progress bar
Clean up look of progress bar

* Widen progress bar
* Increase height of elements contained within the progress bar to
  match my change from the last commit
* Stagger the drag handles so that the time is visible even if they
  are close together. Unfortunately, the clip line appears above the
  start drag handle when they are close together & I can't seem to fix
  this using z-index. I will update this to make the drag handles
  aligned horizontally again, but will nudge them so that the side of
  a handle juts up against the clip line.
Reposition clip line drag handles

Move start handle so that its right side touches the clip handle.
Move stop handle so that its left side touches the clip handle.
Fix side margins

Don't indent the sample editor progress bars.
Improve background colours/shadows of progress bar
Add gradient to selected bar in progress bar
Improve styling of drag handles
Merge branch 'style-the-page'