Topic/psc release

PR pertaining to issue #13.

This does not come without caveats however. For one, `psc-release` relies on a file naming convention of the Github asset files. I am not sure if this is a same assumption to make. Perhaps @paf31 can chime in on this matter. Basically, I am referring to ethul/psc-release#2, and if it's safe to assume the mapping from platform name to PureScript asset filename.

Also, @bodil, I think the addition to the README here may need a bit of tweaking. If you think this PR is a good direction to go, perhaps it would be worth discussing the installation procedure that is described there.

In any case, this is more or less a first attempt. I am open to any suggestions, feedback, or comments.