This uses GHC 7.4 as a reference; i.e. we consider
the versions of boot libraries of GHC 7.4.[12] as the
lower bound we support.

Specifically, w/ GHC 7.4.1, these are the direct dependencies
the cabal solver will come up with (when also forcing
`mtl` to its lower bound):

  array-0.4.0.0
  base-4.5.0.0
  binary-0.5.1.0
  bytestring-0.9.2.1
  containers-0.4.2.1
  deepseq-1.3.0.0
  directory-1.1.0.2
  filepath-1.3.0.0
  ghc-prim-0.2.0.0
  mtl-2.1
  old-time-1.1.0.0
  parsec-3.1.13.0
  pretty-1.1.1.0
  process-1.1.0.1
  text-1.2.3.0
  time-1.4
  transformers-0.3.0.0
  unix-2.5.1.0