Revert "Add constraint "yaml < 0.8.18.2" per snoyberg/yaml#92"
Revert "Add constraint "yaml < 0.8.18.2" per snoyberg/yaml#92"

This reverts commit 301955d14e43721c03634fde899896398eab0dd1.

GregorySchwartz/stackage,k0ral/stackage,phaazon/stackage,ygale/stackage,phadej/stackage,athanclark/stackage,lwm/stackage,alanz/stackage,jonschoning/stackage,fpco/stackage,garetxe/stackage,simonmichael/stackage,wereHamster/stackage,mstksg/stackage,mrkkrp/stackage,spencerjanssen/stackage,judah/stackage,creichert/stackage,DanielG/stackage,clinty/stackage,Shimuuar/stackage,christiaanb/stackage,l29ah/stackage,mgajda/stackage,massysett/stackage,fimad/stackage,jaspervdj/stackage,stackbuilders/stackage,iand675/stackage,Daniel-Diaz/stackage,michalkonecny/stackage,peti/stackage,soenkehahn/stackage,ethercrow/stackage,asr/stackage,brendanhay/stackage,int-index/stackage