Update README.md (#86)
Update README.md (#86)

change installation of sass on mac.
Version via gem is outdated
srauscher/hopglass,gherber/hopglass,plumpudding/hopglass,plumpudding/hopglass,hopglass/hopglass,srauscher/hopglass,Freifunk-Luxembourg/hopglass,gherber/hopglass,Freifunk-Luxembourg/hopglass,hopglass/hopglass