Created test suite for stringLength validator

As per discussion ( https://github.com/nghuuphuoc/bootstrapvalidator/pull/844#issuecomment-55683734 ) added a test suite for the stringLength validator in my fork.
Added option to evaluate length in UTF-8 bytes

Set the utf8Bytes boolean to "true" (defaults to "false") to compare the min/max string length in UTF-8 bytes to facilitate validation for database inserts. By setting the boolean as "false" or not specifying it, is compatible with existing functionality of this validator so this shouldn't affect anyone's existing usage of this validator.

This code is based on that by lovasoa (http://github.com/lovasoa) posted at the following web address on 4/27/2014: http://stackoverflow.com/a/23329386
Merge branch 'master' of https://github.com/thx2001r/bootstrapvalidator into thx2001r-master

Conflicts:
	src/js/validator/stringLength.js
Merge branch 'thx2001r-master'
#874: Add test suite for stringLength validator, thanks to @thx2001r