Added option for CURL to be auto detected and used

There are many hosts that have allow_url_fopen disabled by default. Full disclosure, I used to work for one of them.

The changes made will allow the script to default to curl when it is available, my research shows this is the fastest remote get method, and will fall back to fopen. If neither are available the http request returns false.

I also added a readme file to quickly link to the API docs.