Add a `dogecointip` module a la `bitcointip`

Most of the work was just `s/bit/doge/`.

Not everything that `bitcointip` has is applicable here, mostly because the `bitcointip` bot has an API that `dogetipbot` doesn't.  Also, some of the stuff that works in `bitcointip` doesn't work here for some reason:

 * Automatically hiding bot verifications doesn't work for some weird reason, even though it's the same exact code `bitcointip` uses.

 * Address detection doesn't work either for some reason, although it looks like the only point of that was finding the deposit address.