Typo.
Whitespace.
Update the example that uses 'runGetState' to new API.

Fixes #30.
Typo.
Add haddock annotation, clarify some documentation.
Remove indentation of sample code in haddock.

The rendered layout breaks when a code segment has multiple functions,
it renders without the given indentation. In this commit we set the
base indentation to 0 spaces, and thus it renders correctly.