Embed entities.txt into Mojo/Util.pm

I would like to prepare some script with Mojolicious library embedded into this script. There is App::FatPacker which works great, so i.e. http://cpanmin.us is a fatpacked script.

Mojolicious can be fatpacked too. Unfortunately, there is one problem with standalone file: entities.txt. Mojo::Util searches it in external file and fails if it is missing. It could be fixed easly if the file was embedded in Mojo::Util.

If you don't like this patch, please move this code to separate function, so I could override the loaded in my standalone script, and prevent that Mojo::Util fails if entities.txt is missing.

Thanks.
Looks like `catfile` and `dirname` were only used on this line and no longer need to be imported.