Tell a story about TypeRep

Pico allows the use of Type to classify terms. Of course it does, because it can't distinguish between terms and types. But this is getting ahead of ourselves, as we haven't worked this all out yet. So something has to stop real Haskell programs from doing this. It won't be the type system.

I don't think any of this is too hard, but there needs to be some text about this.
