Added an Autoloader

I added an autoloader to reduce the library's dependence on its location relative to the `include_path`, and to get rid of the annoying `require_once` calls scattered everywhere. To use the library now, you must:

    require 'wherever/the/library/is/Ncstate/Autoloader.php';
    Ncstate_Autoloader::register();

And then you can use any class you want and PHP will magically load it. I have tested the autoloader, but you may wish to perform more testing before you merge this into master. Note that this completely breaks backwards compatibility, so don't publish it as a bugfix release.