Add QuickCheck as a dependency

Otherwise, this happens:
```
$ GHC_PACKAGE_PATH="/app/.halcyon/ghc/lib/ghc-7.8.3/package.conf.d:/app/.halcyon/sandbox/x86_64-linux-ghc-7.8.3-packages.conf.d" \
    mueval -e '1 + 1'
<no location info>:
    Could not find module âTest.QuickCheckâ
    Use -v to see a list of the files searched for.
```