making the bot work without a x-forwarded-for

If the `PROXIED` environment variable doesn't exist, as it won't on systems that don't have it set, it naturally won't be equal to `false`, so `proxied` will be set to true. This causes an error later because the `x-fowarded-for` header in `request.headers` won't exist if the request isn't being proxied, so calling split on it causes

    TypeError: Cannot call method 'split' of undefined

This commit removes the environment variable and checks for the existence of `x-forwarded-for` in `request.headers` to determine whether or not the request is proxied.