Update font-fontawesome.rb
Update font-fontawesome.rb

The font-awesome package extracts to a path with upper 'F' and 'A'. The proposed change is to rectify an issue on systems using a case-sensitive filesystem.
RJHsiao/homebrew-fonts,guerrero/homebrew-fonts,victorpopkov/homebrew-fonts,mtakayuki/homebrew-fonts,sscotth/homebrew-fonts,RJHsiao/homebrew-fonts,caskroom/homebrew-fonts,mtakayuki/homebrew-fonts,alerque/homebrew-fonts,alerque/homebrew-fonts,caskroom/homebrew-fonts,unasuke/homebrew-fonts,sscotth/homebrew-fonts,victorpopkov/homebrew-fonts,guerrero/homebrew-fonts