Improve layout styles with flexbox

[rtlong]

Also, yank out Foundation

[rtlong]

Before

After

Notes

• Album art is "zoomed" to fit square box
• Scroll bar is just inside tracklist section and is styled
• in Player, text element is vertically centered on the play/pause button
• play progress and timer components were separated
  • play progress bar is colored using two colors which are visible
  • updates to the play progress bar are smoothed using the CSS transition property
  • this includes when clicking on it, which I think adds a nice touch
• tracks are centered horizontally
• tracks are centered vertically when list is short enough (maybe this isn't what we want, idk, but I feel it helps to emphasize the tracks being the focal point of the UX so far)
• track hover opacity change is also transitioned smoothly using transition
• track title and artist names are length-limited so they do not wrap to more than 1 line with an ellipsis should that limit take effect

[rtlong]

Also, please try to ignore the restart stuff here, I merged that in already: #9

[namick]

All good. Big win.