Cleaned up CSS and HTML, fixed sidebar click bug

Swapped out the #header for a normal <header> tag, added a proper
footer, and made some other minor changes. Merged a few CSS styles as a
result.

Fixed the sidebar bug, where pjax was not stopping the event from
bubbling.
Added handling for the top next/prev buttons
Commented out excess fonts, fixed seek bar positioning
Updated pjax
Added proper spacing for player screen