Update browser_helper.rb and warn for old Firefox and Safari
Use 'browser' gem for detection instead of custom regex
Update activity-monitor to use gem 'browser' instead of 'user_agent_parser'
Fix activity-monitor and lib/cdo extension
Code review feedback
Do..end -> braces
Merge branch 'staging' into browser-support-warnings
Merge pull request #59 from code-dot-org/browser-support-warnings

[Finishes #69042946] Browser support warnings