Revert "haskell-pandoc-citeproc: drop obsolete versions 0.4 and 0.5"

This reverts commit d3b2c3f46c5bce8466e0813351afcaf2fe8fa92d.

@peti I'm reverting this commit until a resolution is found that allows
Hakyll to build.  I've confirmed that reverting it here fixes the build
error.