Allow to use URL for user rule, such as a raw gist

A simple change to allow using URL for user rule import, so that we can use a remote file for user rules, for example, I am using a raw gist URL.

The idea is to host own custom rules in the web, mostly, my own gist.

Next idea might be creating a alfred workflow for creating rules into a GIST and fire the PAC file generation directly after the custom rules changed.

The gitignore file was created in my local to avoid some files get checked in, you can avoid it if you don't like it.