typo: version 'latest'
update firefox-ux to use version 'latest'
update google-chrome-beta to use version 'latest'
update google-chrome-dev to use version 'latest'
update papers2 to use version 'latest'
update firefox-nightly to use version 'latest'
Merge pull request #344 from rolandwalker/use_latest

convert several Casks to version 'latest'