Finished converting webvtt_string to use webvtt_byte. Applied changes to cue text parser portion and C++ bindings. However, the implementation of webvtt_string_getline still needs to be finished.
Merge with cait refactor and fix minor bugs.
Minor bug fixes.
Now calling webvtt_parse_cuetext from webvtt_parse_chunk -- parse_cuetext now has the webvtt_parser passed to it, so it may return errors to the application. removed payload from the webvtt_cue struct, as we are using the line_buffer to store the payload, and removing it after parsing. can change this if necessary later.