change the hostname in the version strings from allmydata.org

[zooko]

Our protocol versioning scheme uses URLs to indicate specific versions of things. Those URLs currently have hostname "allmydata.org" but we've moved to make "tahoe-lafs.org" our primary hostname for the open source project. Should we change those URLs? Would that confuse clients that are using those URLs for version indicators -- would they think that this means a new (and presumably incompatible) version of the protocols in question and thus refuse to interoperate or something?