Added callback onElementValidate and possibility to customize errorMessa...

Added callback onElementValidate and possibility to customize errorMessage through errorMessageTemplate config param

### Usage example

```html
<form id="myTestForm" action="index.html" method="POST">
    <div>
        <label for="user">User</label>
        <input id="user" name="user" data-validation="required" data-validation-error-msg="The field user is required">
    </div>
    <div>
        <label for="birthday">Birthday</label>
        <input id="birthday" name="birthday" data-validation="date" data-validation-format="dd/mm/yyyy" data-validation-error-msg="Data inválida" data-mask="00/00/0000">
    </div>
    <div>
        <label for="free">Free</label>
        <input id="free" name="free">
    </div>
    <div>
        <button type="submit">OK</button>
    </div>
</form>
<script src="js/jquery.min.js"></script>
<script src="js/form-validator/jquery.form-validator.min.js"></script>
<script>
    $.validate({
        form: '#myTestForm',
        validateOnEvent: false,
        validateOnBlur: false,
        showHelpOnFocus: false,
        addSuggestions: false,

        // One way
        errorMessagePosition: 'custom',
        errorMessageCustom: function(form, title, errorMessages, conf) {
            console.log(errorMessages);
        },
        // end One way

        // Another way
        errorMessagePosition: 'top',
        errorMessageTemplate : {
            container: '<div class="{errorMessageClass} alert alert-danger">{messages}</div>',
            messages: '<h3>{errorTitle}</h3><ul>{fields}</ul>',
            field: '<li>{msg}</li>'
        },
        // end One way

        onError: function(f) {
            console.log(f, 'onError - Validation failed');
        },
        onSuccess: function(f) {
            console.log(f, 'onSuccess - The form is valid!');
        },

        // Callback Validate by field
        onElementValidate: function(isValid, field, validation) {
            if(validation !== null)
                console.log(isValid, field, validation);
            else
                console.log(field, 'without validation');
        }
    });

    $('#myTestForm').on('submit', function(ev){
        ev.preventDefault();
        console.log('submit!!');
    });
</script>
```