Snapshot testing

[Magellol]

It might be a good idea to use snapshot testing to test the TS output. Something like https://hackage.haskell.org/package/hspec-golden-0.2.0.0/docs/Test-Hspec-Golden.html — I've given it a shot and it was easy to setup for a basic configuration. 922106f

Perhaps we could also take it a notch further and write a specific golden config to output .ts files and test them against the TS compiler or something to verify they are type safe? Perhaps prettify them as well somehow.