incorporate feedback on consistency of SDK Quickstart with API doc

These commits incorporate feedback from Mike Asthalter, Information Developer for Cloud Load Balancers. Mike's detailed comments are at https://jira.rax.io/browse/DEVDOC-93. Primary change is addition of "rate interval" to the text of the Set limits section. Most other changes relate to style, such as using lower case to refer to nodes and lists. 

Also, I added a link to `Quickstart for Cloud Servers </docs/cloud-servers/getting-started/>`_ but I have no way to test it; please make sure that link is valid.