Add thank you to SauceLabs to README
Add thank you to SauceLabs to README

As a condition for using Sauce Labs, they asked us to put a thank you on our repo.

Shall we leave this in a branch until we've had a look at it and what it can do for us?
pg-irc/pathways-frontend,pg-irc/pathways-frontend,pg-irc/pathways-frontend,pg-irc/pathways-frontend