Fixes bracket match in rule function

When adding a custom type e.g. "isValid[\\[0-9A-Za-z\\]\\+]" using form validation module, I found it got the wrong match "[0-9A-Za-z" as the regular expression, so I prefer using greedy match.

And here is the source code:
```js
var validationRules = {
    username: {
        identifier: 'username',
        rules: [
            type: 'isValid[\[0-9A-Za-z\]\+]',
            ...
        ]
    }
};
$.fn.form.settings.rules.isValid = function (value, reg) {
    var regExp = new RegExp(reg),
        matches = regExp.exec(value);
    return matches && matches[0] === value;
};