Update alfred recipe

Alfred is no longer distributed as .dmg but instead as a zip file.
Update Google Chrome checksum
Update Dropbox checksum
Parametrize Firefox recipe

Also update the checksum.
Update HipChat recipe to install newer version
Update LastPass checksum
Parametrize Skype recipe

Also update the version.
Update VLC version
Parameterize Safari preferences recipe
Update iTerm2 download link
Removed old flux attributes
Merge branch 'master' into update-alfred-recipe
Use Homebrew Cask for Alfred
iTerm2 recipe uses Homebrew Cask
VLC recipe uses Homebrew Cask
Google Chrome uses Homebrew Cask
Dropbox recipe uses Homebrew Cask
Firefox recipe uses Homebrew Cask
HipChat recipe uses Homebrew Cask
Skype recipe uses Homebrew Cask