Added pause button and key ('esc').

Other changes:
- Added cross-browser font support (thanks to Font Squirrel).
- Added a mute state instead of relying on the 'src' element (needed for 'pause').
- Default key actions are prevented prior to asset loading (e.g. 'esc' will cancel loading in Chrome).
- Disabled text selection.
- Added cursor changes for icons and popup text.

Signed-off-by: Jeffrey Han <itdelatrisu@gmail.com>