New snapshot with removal of at-risk items

[gkatsev]

This is adds a new snapshot that can be used for a PR when moving forward. It removes the at-risk items.

Live overview: https://htmlpreview.github.io/?https://github.com/gkatsev/webvtt/blob/at-risk-snapshot/archives/2019-05-02/Overview.html
Live changes: https://htmlpreview.github.io/?https://github.com/gkatsev/webvtt/blob/at-risk-snapshot/archives/2019-05-02/changes.html
Live diff: https://htmlpreview.github.io/?https://github.com/gkatsev/webvtt/blob/at-risk-snapshot/archives/2019-05-02/diff.html

[gkatsev]

This PR creates a new snapshot based on #449 which removes the at-risk items. I'm going to close this since there's now #460, #461, #470, #471, and #493 that we'd want to get in. Plus, with the new process, we may not need/want to remove these outright. Either way, I think a new one of these would be warranted.