fix(coreos): tune etcd to address high disk i/o environments
fix(builder): limit cpu shares to 800
docs(managing_deis): provide login instructions

Add a page to the docs to explictly define how to connect to a
cluster.
Merge pull request #2643 from gabrtv/etcd-fixes

Tune etcd to address timeouts and builder issues
Merge pull request #2649 from mboersma/login-instructions

docs(managing_deis): provide login instructions