Recreating plugin instance if new options were provided.

In previous version setting new text didn't take effect id it was set second time:
$.isLoading({text: 'Loading user data...'});
$.isLoading('hide');
$isLoading({text: 'Sending message...'});
caused showing of "Loading user data..." loading message twice.

I've added recreation of plugin instance if new "non-hide" options were provided. This will allow to change options dynamically.