rename rest-client.rb

to `wiztoolsorg-restclient.rb`, per naming rules in `CONTRIBUTING.md`.
This requires making changes to the test suite, as the tests used this
cask.  Imported special test Casks for the relevant test no longer has
a dependency on real Casks.
Merge pull request #3155 from rolandwalker/rename_rest-client

rename rest-client.rb