Fixes #118 - Correct assertions, add safety assertions, wrap lines

- Assert error count before asserting error conditions, for safety
- Assert WEBVTT_INVALID_CUESETTING rather than
  WEBVTT_INVALID_CUESETTING_DELIMITER, which should be deprecated.
- Wrapped lines to 80 columns
Merge pull request #118 from caitp/issue-118

CueSettingPosition.BadDelimiter incorrect assertion