remco v0.4.0

This release includes the zookeeper backend and some bug fixes.

Bug fixes

• 7afb322 redis backend: fixed a possible panic when calling Close()

New Backends

• [e2f146d 163a245 eaa69fa] Zookeeper

Other Changes

• bf2bdeb list the env backend in the docs
• 8aab64a use context based cancelation instead of stop channels
• 8a7b141 etcd: removed the basic_auth flag - use basicAuth if a username and password is provided