Convert NodeJS Library to typescript

I'd like us to consider migrating the NodeJS library to typescript. I feel this would simplify the existing libraries and build system. The typescript library would just need to be compiled down to javascript as part of the build system.

This will:

• Introduce compile time type checks to help catch bugs
• Provide better type documentation for consumers of the library
• Include better typescript tests in the build
• Allow us to merge the nodets and nodejs lib folders
• Synchronize the javascript codebase with the type definitions (currently, there is an external project at DefinitelyTyped to provide typescript types for the nodejs lib)

If the maintainers think this is a good idea, I'd be happy to take a stab at it.