Initial simple version of unifier.

This is still quite rough - improvements to be made:
* make the thing look pretty
* support function syntax (->) and other operators
* a more effective visualization
* maybe add typeclasses
* clean up the code

Installation instructions:

This code uses [ghcjs](https://github.com/ghcjs/ghcjs) - just using the
vm they provide is the easiest way to get started.

Once you have the vm set up clone this repo then run `make` from inside.
Start the vm's server with `vagrant ssh -c warp`, then visit
localhost:3030.