feat(etcd): Default server listen and client listen to advertised IPs

Map the advertised IP to the listening IP by default. This will make
things nicer for the user.
fix(README): use 127.0.0.1 everywhere

0.0.0.0 used to be the default advertised ip, fix this everywhere.
feat(README): document -cl flag
Merge pull request #151 from philips/listening-ip-cleanups

Listening ip cleanups