Merge pull request #21 from ocharles/master

Increase upper-bound on 'free' to 4.2
Updated documentation
Changed `foldlFree` and `foldMFree`

They now more greatly resemble their `pipes` counterparts
Polished source code for `dropFree`
Temporarily removed `foldFree` and `foldMFree`

I think I've finally sorted out the last remaining issues with the `foldl`
library, and when I do I woulld like to reintroduce these to take a `Fold` as an
argument.
Updated documentation
Polished source code
Changed version to 2.0.1

The main difference is an increase in the upper bound of `free`, but after
reviewing the differences in the `free` package I doubt this will break
downstream code.
Increase upper-bound on free to 4.3