Remove incorrect arg param to convertCueToDOMTree().

For some reason we were passing filterJson to the
convertCueToDOMTree() function. This function doesn't accept
anything like that.
Add regions to processing model.
Add run processing model functionality to util.js
Rewrite cue2json.js.

- Rewrote cue2json to simplify it.
- Added functionality output JSON generated from the
processing model.
Add basic processing model test.
Update README.md

- Add info about the processing model now handling regions.
- Add info about the new cue2json.js script.
Refactor processing model.
Determine bidi of the first paragraph of a cue.
Update and refactor processing model.