Make a release

[k-bx]

I see in master that base is required only < 5, while if you do cabal get shelly-1.6.8.1 you'll see a piece like:

  if impl(ghc >= 7.6.1)
    build-depends:
        base >= 4.6 && < 4.9.1
  else
    build-depends:
      base >= 4 && < 5

There's also some problem with the directory package:

➜  Downloads  stack install --resolver nightly-2017-02-03 shelly-1.6.8.1

Error: While constructing the build plan, the following exceptions were encountered:

In the dependencies for shelly-1.6.8.1:
    base-4.9.1.0 must match >=4.6 && <4.9.1 (latest applicable is 4.9.0.0)
    directory-1.3.0.0 must match >=1.1.0.0 && <1.3.0.0 (latest applicable is 1.2.7.1)

Plan construction failed.

[gregwebs]

There is a newer release now.