Typescript migrations

[armaniferrante]

Currently the migrations feature is javascript only.

[armaniferrante]

Might be able to use something like https://github.com/TypeStrong/ts-node, or we can just run tsc + node seprately (I prefer the latter I think, so that we can avoid an additional dependency).

[armaniferrante]

We can just do what we do for typescript tests. I.e. check for a tsconfig and a .ts extension on the deploy script, and if they exist, run the typescript flow here https://github.com/project-serum/anchor/blob/master/cli/src/main.rs#L1380.

[armaniferrante]

Addressed by #132.