Revert "allow markdown testsuite to fail (snoyberg/markdown#39)"
Revert "allow markdown testsuite to fail (snoyberg/markdown#39)"

This reverts commit e71a2158473892a0dbf95878c2f59d2494314cc5.

simonmichael/stackage,jonschoning/stackage,Daniel-Diaz/stackage,mrkkrp/stackage