Add typescript types

[hueniverse]

• Copies the DT types for 10.2 as base
• Fix client constructor
• Fix tests
• Add missing events and client properties
• Fix stats type

[hueniverse]

Tests have always been flaky. Someone with admin rights needs to rerun them to verify.

[hueniverse]

Thanks @cjihrig!

[hueniverse]

Who does the merging and publishing?

[devinivy]

I can make it happen, but I could use a hand from the TS crew— do we consider this a minor or major release?

[Marsup]

From the diff, I'd say minor. There's a breaking change on the stats property, but DefinitelyTyped's was wrong on this part as it's not a function, so if it triggers some errors, I'd say that's actually a good thing.