GitLab

According to the [creator's twitter](https://twitter.com/mjackson/status/770427936449101824) and the [npmcdn's website](https://npmcdn.com/) the project was renamed to unpkg to avoid trademark issues.

Not sure if I fully understand these, but I sensed inconsistency
* enter nodes are not defined anywhere, but placeholders are mentioned
  everywhere
* catmull-rom changes described restoring the old behavior, but showed
  the new behavior
* random fixes