Document effective use of the gem

[boardfish]

There are a few things this has helped us do at @raisedevs:

• Record VCR cassettes
  I've already got a quick overview for this, but more detail would be good, especially for throwaway variables you use just to provide creds to a recording session. Improving that workflow really deserves its own issue.
• Use the Rake task in Scripts to Rule Them All
  This repo's probably a good platform to shout about that strat.