README should specify requirements

[dmcassel]

• What version of MarkLogic is required? Is 8.0-1 good enough, or does it need 8.0-3?
• What version of Node?
• Any other requirements to run this?

[xquery]

there have been many fixes since 8.0-1 ... optimally 8.0-4 (or 8.0-3).