Test failure with GHCJS 8.4

[ElvishJerricco]

Full log: https://gist.github.com/ElvishJerricco/f318829d9cccb6f0ccaa4888dae8a7c5

Considering the actual and expected outputs appear identical, I'd wager this is a GHCJS bug, but I'm not sure. /cc @luite

[sergv]

@ElvishJerricco It may be related to #20. There are Doubles so it's possible that they're print the same but actually are not ==.