Conservatively allow Haml 4.x. #434.
Conservatively allow Haml 4.x. #434.

`stacktests` (all) passes with Haml 4.0.1, so it seems to be safe
to allow it. This commit allows Haml 4.x along with 3.1.x (there is
no Haml 3.2, etc.) but not 5.0+. Haml has switched to semver with the
4.0 line, so allowing 4.x should be safe.

blueboard/surveyor,bricesanchez/surveyor,HeHStudy/surveyor,fhisamoto/surveyor,blueboard/surveyor,lampo/surveyor,fhisamoto/surveyor,Guestfolio/surveyor,anitsirc/surveyor,bricesanchez/surveyor,lampo/surveyor,anitsirc/surveyor,serracorwin/surveyor,alanjcfs/surveyor,serracorwin/surveyor,lampo/surveyor,Guestfolio/surveyor,HeHStudy/surveyor,alanjcfs/surveyor,markedmondson/surveyor,fhisamoto/surveyor,NUBIC/surveyor,blueboard/surveyor,fhisamoto/surveyor,anitsirc/surveyor,alanjcfs/surveyor,serracorwin/surveyor,HeHStudy/surveyor,Guestfolio/surveyor,blueboard/surveyor,bricesanchez/surveyor,NUBIC/surveyor,anitsirc/surveyor,Guestfolio/surveyor,bricesanchez/surveyor,markedmondson/surveyor,markedmondson/surveyor,alanjcfs/surveyor,lampo/surveyor,NUBIC/surveyor,HeHStudy/surveyor