Remove support for environment variables, use cache files instead

[troglobit]

The environment variables are useless.

IP, and any other information, should instead be be read from the cache file.

[troglobit]

Closing this as won't fix -- there are potentially many .cache files. Having all the information readily available as environment variables doesn't hurt. Also, not all cache files will be updated when the callback is executed. Only the environment variables can be trusted.