Add repNM for range repetition

[pgrandjean]

This is a proposal to add operator repNM that repeats a parser in a range(n, m). In other words, repNM would ensure that a parser is run at least m times and up to n times.

This proposal is a follow up on comments and code in Stackoverflow by Jörg W Mittag.

I have some working code that I would like to submit in a PR, if it is OK to continue with this proposal.

[SethTisue]

I can't think of a reason this wouldn't be accepted

[pgrandjean]

Great! Thank you.

[pgrandjean]

PR #245 merged