Change rvmrc to ruby-version and ruby-gemset
More updates for Ruby 2.1 compatibility
Update Airbrake, i18n and Shotgun gems
Rename powenv to powrc
Add ActiveSupport as Object#present? is used
Merge branch 'ruby-upgrade' into release/v3.35
Fix ruby 2.1 compat issue

WEB-16456
Add lost installation instructions
Fix indentation