Create method ruby_file?
Create method ruby_file?

Both formula_files and cask_files need to check whether a file is
a Ruby file. Also, use this method in formula_file? and cask_file?

Homebrew/brew,JCount/brew,Linuxbrew/brew,Homebrew/brew,sjackman/homebrew,reitermarkus/brew,MikeMcQuaid/brew,nandub/brew,claui/brew,vitorgalvao/brew,claui/brew,claui/brew,claui/brew,Linuxbrew/brew,MikeMcQuaid/brew,Linuxbrew/brew,reitermarkus/brew,nandub/brew,vitorgalvao/brew,mahori/brew,EricFromCanada/brew,sjackman/homebrew,MikeMcQuaid/brew,vitorgalvao/brew,reitermarkus/brew,konqui/brew,Linuxbrew/brew,mahori/brew,JCount/brew,konqui/brew,sjackman/homebrew,EricFromCanada/brew,Homebrew/brew,vitorgalvao/brew,JCount/brew,mahori/brew,EricFromCanada/brew,JCount/brew,sjackman/homebrew,reitermarkus/brew,Homebrew/brew,nandub/brew,konqui/brew,konqui/brew,MikeMcQuaid/brew,nandub/brew,mahori/brew,EricFromCanada/brew