v1.2

- Remove ability to load a track from url params (for now).
- Add `secret-token` attribute to element with using the `ascii-player` class.
- Introduce `AsciiPlayer()` with methods `init()`, `initTracks()`, `getTrack()`, `renderPlayer()`.
- Rename old `asciiPlayer` class to `Player`
- Add event listener on progress bar for clicks, and update progress bar based on track position (Fixes #1)