There are currently two functions that could blow-up the stack. [One](https://github.com/TheBlackBeans/beans/blob/4af1cc6d9d65096b48aaf5ddaf403f70669cba57/src/regex/parsing.rs#L479-L549) in the regex module, the [other](https://github.com/TheBlackBeans/beans/blob/4af1cc6d9d65096b48aaf5ddaf403f70669cba57/src/parser/earley.rs#L1111-L1180) in the parser. Both of these could be replaced with a loop, which could prevent the danger.
