Update cask name for WebP Quick Look

`webp-quicklook` → `webpquicklook`

This cask was renamed earlier this month:
https://github.com/caskroom/homebrew-cask/commit/3223de58872050923b311422d5d6a6af92f81440
Merge pull request #22 from coox/master

Update cask name for WebP Quick Look