Remove stray underscore leftover. Might fix #3153...
Add tests to exercise invalid/expired cert code, check for context fetch errors.

cleanupIdentities takes a proper failure callback now.
Updates to include new platform and config support

General clean up of the entire README.md file - first several sections for installing, configuring, and running the automation.
Merge pull request #3168 from mozilla/issue_3153_invalid_certs

Issue 3153 invalid certs