Convert to TypeScript

[balupton]

These deps need to be converted first:

• ambi
• https://github.com/bevry/unbounded

These deps are not necessary anymore in a typescript environment:

• eachr
• extendr

[balupton]

this was pretty much entirely done on a local copy that I have back in 5 December 2018

[balupton]

note that in march 2017 there was also a bunch of work done to implement promises as well:
https://github.com/bevry/taskgroup/tree/feature/promise

#25