Regenerate Constants.h
Fix running RSpec on Travis
Emphasize in the APT installation documentation that the user is only supposed to add one of the APT lines, not all of them
When displaying the language menu in passenger-install-nginx-module, advise the user to enable UTF-8 in his terminal in case the menu does not display correctly
passenger-install-nginx-module: check whether there is already an existing Nginx installation and warn the user about it