Appveyor

[jennybc]

• Turn it on
• Have a successful nontrivial build

[richfitz]

Jenny - I think you'll have to flip the switch in appveyor, or perhaps make me an admin on the rsheets organisation

[richfitz]

hmm, I am already an admin, and have added appveyor but it doesn't show up on the appveyor project page. Perhaps time will fix this...