Don't split on options if key isn't a string.
Add WebVTTParser.clear().

Clears the state of the WebVTTParser in order have a fresh
state to start parsing again.
Run vtt.js on PhantomJS from Node.

- Created NodeVTT which runs VTT things on PhantomJS from Node.
- Cue2Json now utilizes the ParserRunner.
NodeVTT should be able to parse different VTT sources.

- Simulate streaming parsing by passing an array of Uint8Arrays.
- Parse from a file.
- Parse from a string.
Fixes.