Maximum length message is misleading

The [return message](https://github.com/nowsecure/owasp-password-strength-test/blob/master/owasp-password-strength-test.js#L52) for the maximum length message is misleading

"The password must be fewer than ' + owasp.configs.maxLength + ' characters."

should say something like the following:

"The password must be **_at most**_ ' + owasp.configs.maxLength + ' characters."
