Nodes must persist which bucket in the hashring they belong to

[mattbostock]

Using Jumphash, nodes are represented by buckets.

In order to minimise the amount of data that moves when nodes are added or removed, nodes must remember which bucket they belong to and use that same bucket when they reconnect to the cluster.

Found during the implementation of #149.

This limitation is mentioned in the abstract for Jumphash:

Its main limitation is that the buckets must be numbered sequentially, which makes it
more suitable for data storage applications than for distributed web caching.

...the consequences of which were not clear to me when deciding on #27.