Cleaned up some memory leaks, got rid of gsequence, improved test macro to free memory that it allocated

Moved parse_state_t into internal.h, had to add some things for Warth's recursion. More documentary comments.

All unit tests written except chain and chainl. Removed left_factor_action, we'll handle left-recursion with our caching strategy.

Fixed inconsistent signature of charset parser, registered (still stubbed) unit tests so the build doesn't break :)