Revert "Handles unlimited range numbers"

This reverts commit 5ef767c4e11a795a33739619a6b6dbd21c59d90a.
Handles unlimited rangelength values

WTForms uses -1 to denote no minlength/maxlength value. This makes the rangelength
validators incorrect. This patch falls back to minlength/maxlength
validation when one of the length values is -1.