Expand on documentation and examples

[copumpkin]

I'm thinking:

1. A simple sketch (in code structure, perhaps without implementations) of what it would look like for Hydra or NixOps to use nix-exec behind the scenes
2. An example of the IO monad bind machinery doing something non-complex. Without do notation or an example that uses join/map, I'm not sure how to use them

These two would do wonders to help clarify what more complex things would be doing here.

Also, it might be good to explain what the endgame is here. Do you envision this getting merged into Nix proper? It seems like the sort of thing that might make sense to have in mainline, but you might also not want to deal with yet another PR 😄

[shlevy]

Documentation ideas are good, will try to find time for that. As for endgame, hnix or similar and having the nixexpr evaluator with decent library support will address most of the needs this fills. As of now, though, keeping it updated and self-contained is enough for me.