Core Raft API operations over HTTP. Clients are currently stateless, but you
may maintain connection pools going forward. In general, one creates a client
using (connect) and uses that client as the first argument to all API
functions.

Every operation may take a map of options as an optional final argument.
These options are remapped from :clojure-style keys to their Raft equivalents
and passed as the query parameters of the request; with the exception of a
few keys like :timeout; see http-opts for details.

Functions with a bang, like reset!, mutate state. All other functions are
pure.

Some functions come in pairs, like get and get*.

The get* variant returns the full etcd response body as a map, as specified
by http://coreos.com/docs/distributed-configuration/etcd-api/. Note that
values are strings; verschlimmbesserung does not provide value
serialization/deserialization yet.

The get variant returns a more streamlined representation: just the node
value itself.