Add contributing guidelines
Add contributing guidelines

RallySoftware/boxen-nginx,weyert/puppet-nginx,RallySoftware/boxen-nginx,TORO-IO/puppet-nginx,jaredreynolds/puppet-nginx,RallySoftware/boxen-nginx,zachpendleton/puppet-ngx_openresty,jaredreynolds/puppet-nginx,boxen/puppet-nginx,TORO-IO/puppet-nginx,grosser/puppet-nginx,jaredreynolds/puppet-nginx,grosser/puppet-nginx,boxen/puppet-nginx,weyert/puppet-nginx,n0ts/puppet-nginx,zachpendleton/puppet-ngx_openresty,zendesk/puppet-nginx,n0ts/puppet-nginx,n0ts/puppet-nginx,TORO-IO/puppet-nginx,Paulche/puppet-nginx,Paulche/puppet-nginx,Paulche/puppet-nginx,zendesk/puppet-nginx,weyert/puppet-nginx,boxen/puppet-nginx,zendesk/puppet-nginx