Fixed error message for regex rule validation

In Laravel 4, the validation rule that does regular expression matching is called "regex", not "match".

Example code:
$validator = Validator::make(
	array('xyz'=>'some text that will fail the validation'),
	array('xyz' => 'regex:/\d\d/')
);
if( $validator->fails() )
	return Response::json($validator->messages()->all(':message'), 400);

Before this patch, this will return:
"validation.regex"

After this patch, this will return:
"The x format is invalid."