These functions are from Language.GraphQL.Schema.
There are actually only two generic types in GraphQL: Scalars and objects.
Enum is a scalar value. According to the specification enums may be
serailized to strings. And in the current implementation they used
untyped strings anyway, so there is no point to have differently named
functions with the same implementation as their scalar counterparts.

Mostly basic documentation. Fixes #4.

... to distinguish between minified and pretty printing.

- Remove generated documentation leaving only documentation sources.
- Add CI job checking that the tutorial is up to date.