WIP: Switch to using API V1

There are a number of formerly *deprecated* API calls in v0 that are now **disabled** (e.g. withdraw). This will migrate the entire library over to the v1 API. Since v1 and v2 are also quite similar, the switch to v2 should be as simple as updating the checksum calculation (it now includes the URL as part of the sum) and updating the individual calls from `/api/1/<foo>` to `/api/2/<foo>`.

There are going to be a ton of changes involved here, so I'm opening up the PR very early on so that you don't suddenly get swamped with one monster pull request once everything is done.