* Update link to speedtestservers and server_id
The link to the speedtestservers seems to be broken. The new link does work. Also the server_id seems to be mandatory at this point. So this sets the server_id to be required and in the example configuration.yaml inserts an example server_id.
* Removes sever_id from configuration.yaml
Removes sever_id from configuration.yaml. It's not necessary if server_id is optional.
* Changes server_id to be optional again
