Look into implementing loop protect

[Loop protect](https://github.com/jsbin/loop-protect) could help guard against bad code.

**Update**
Loop protect is pretty basic. If I ever want to use something like it, I would probably want to contribute back to the project to make it a bit more robust.

Start by reviewing the linked loop-protect project and its limitations, then determine how it would fit into gistbook. The issue does not name any files, tests, or entry points; done would require a robust approach to guarding against bad code rather than adopting loop-protect as-is.

Written by the indexing model from the issue text.