Change to list comprehension

The main body of `inSections` was too small for a do statement, and list
comprehension seem to fit its one action over a list.
Rename s to sections
Make helper funtions feel less like one-liners
Add type signature to less generic functions

The `groupBy'` function have two different types it handles, so a type
signature wouldn't help it much.
Move more important functions up to the top
Merge branch 'refactor'
Version bump to 0.3.2