update all references to new caskroom org home

global replace of:
  'phinze/homebrew-cask' -> 'caskroom/homebrew-cask'
  'phinze/cask' -> 'caskroom/cask'
  'phinze/homebrew-testcasks' -> 'caskroom/homebrew-testcasks'

and various other specific places that needed updates

<3 the homebrew-cask community!
Merge pull request #4163 from caskroom/migrate-to-org

update all references to new caskroom org home