Add dead end clarification to chompIf doc

[neurodynamic]

Just a suggestion here. I think because of how "if" and "while" usually work in programming languages, I assumed chompIf was like a "parse one or move on" rather than a "parse one or dead end"-type thing, and spent a bit trying to figure out how to do a chompOne function before realizing my mistake. I figure this might prevent others from possibly making the same error.

For me, at least, I think chompOne might be a clearer name, even though I can totally see how chompIf makes sense.