build via cabal sandboxes instead of cabal-dev
explain why there is both a Makefile and a .cabal
ignore base, resolves #2 (for now)

To allow tests to pass with recent versions of base, I removed the upper
bound. To allow cabal-rangefinder to accept the existing lower bound,
cabal-rangefinder now ignores "pinned" packages such as base. I'll add
more pinned packages to the list as I discover what they are. "Cabal",
perhaps?