Replaced a few TODOs by the variables they were refering to, updated the README

I noticed a few links documenting variables that were not being set by the userscript, so I just added them in. I have not extensively tested my modification, although it doesn't seem to have broken anything so far.
Do you think firefox will connect to a default server if it can't connect to the user-supplied one ? I took this remark into consideration when I remade my modifications into several commits, and replaced "localhost" with an empty string.

I also thought that you were going to add the `geo.wifi.url` variable to the script anyways, since it was mentioned in a `TODO` comment. I realize that since `geo.enabled` is set to `false`, there's no point in modifying that URL, but I thought you mentioned it anyways because you wanted to ensure that the browser would not leak information if the user (or arbitrary code) came to change that one variable that controls everything.