Normalize asset names.

Library/Homebrew/cask/test/cask/installer_test.rb

Library/Homebrew/cask/test/support/Casks/container-7z.rb

Library/Homebrew/cask/test/support/Casks/container-bzip2.rb

Library/Homebrew/cask/test/support/Casks/container-cab.rb

Library/Homebrew/cask/test/support/Casks/container-dmg.rb

Library/Homebrew/cask/test/support/Casks/container-gzip.rb

Library/Homebrew/cask/test/support/Casks/container-lzma.rb

Library/Homebrew/cask/test/support/Casks/container-pkg.rb

Library/Homebrew/cask/test/support/Casks/container-rar.rb

Library/Homebrew/cask/test/support/Casks/container-sit.rb

Library/Homebrew/cask/test/support/Casks/container-tar-gz.rb

Library/Homebrew/cask/test/support/Casks/container-xar.rb

Library/Homebrew/cask/test/support/Casks/container-xz.rb

Library/Homebrew/cask/test/support/Casks/gzipped-asset.rb

Library/Homebrew/cask/test/support/Casks/rar-container.rb

...ry/Homebrew/cask/test/support/Casks/sevenzip-container.rb

...ary/Homebrew/cask/test/support/Casks/stuffit-container.rb

Library/Homebrew/cask/test/support/Casks/tarball.rb

Library/Homebrew/cask/test/support/Casks/xar-container.rb

Library/Homebrew/cask/test/support/binaries/cabcontainer.cab