Issue title: AlphaNumeric Option please
 Issue body: To reproduce the error or describe your requirement with a jsfiddle url would be appreciated:
- Fork this with vanilla JS component: https://jsfiddle.net/nosir/kbaxx64s/
- Fork this with React JS component: https://jsfiddle.net/nosir/gLLsrxxf/

If it's mobile related, please specify your device and environment.

 Comments: 
 Comment 0: I second this. Great library, but eventually I had to find alternatives due to its missing alpha-numeric filter option. Our use case can allow only a subset of letters (no capital O or I since they can easily be confused).
 Comment 1: Having this option would be really helpful.
 Comment 2: Here is a quick fix that i put in my script, it's reactive to the input, so not as clean as when you use numericOnly, but it does the trick. 

            $('#id').on('keyup', function () {
                var input = $(this).val();
                var regex = input.replace(/[^\w]/g, "");
                $(this).val(regex);
            })
{'source': 'GithubIssues', 'repo_name_with_owner': 'nosir/cleave.js', 'issue_id': 406705388, 'repo_stars': 18335.0}