Warn on no Procfile use, don't mention Webrick
Warn on no Procfile use, don't mention Webrick

While someone __may__ be using webrick they may also be puma or some other webserver with an integrated rack handler. Make the error more generic. The webpage was updated to say that a `Procfile` is best practice. It still talks about WEBrick but this is secondary.

donnykurnia/heroku-buildpack-ruby,ericboehs/heroku-buildpack-ruby,Genius/heroku-buildpack-ruby,ekaranto/rails4-bluemix-buildpack,ericboehs/heroku-buildpack-ruby,jonseaberg/heroku-buildpack-turbo-sprockets,ekaranto/rails4-bluemix-buildpack,jumptvs/BP_Ruby,brightbytes/heroku-buildpack-ruby-without-assets-precompile,jumptvs/BP_Ruby,beydogan/ruby-buildpack,tenjikinc/heroku-buildpack-ruby,moneyadviceservice/heroku-buildpack-ruby-bowndler,markaschneider/heroku-buildpack-ruby-ffmpeg-sox,zoomer/heroku-buildpack-ruby-bower,orenyk/heroku-buildpack-ruby,jonseaberg/heroku-buildpack-turbo-sprockets,heroku/heroku-buildpack-ruby,heroku/heroku-buildpack-ruby,donnykurnia/heroku-buildpack-ruby,tpope/heroku-buildpack-ruby-tpope,pkgr/heroku-buildpack-ruby,cloudfoundry/ruby-buildpack,moneyadviceservice/heroku-buildpack-ruby-bowndler,cloudfoundry/ruby-buildpack,cloudfoundry/ruby-buildpack,pilotcreative/heroku-buildpack-ruby,bwaite-jaroop/heroku-buildpack-ruby,qnyp/heroku-buildpack-ruby-bower,bwaite-jaroop/heroku-buildpack-ruby,ekaranto/rails4-bluemix-buildpack,cloudfoundry/ruby-buildpack,brightbytes/heroku-buildpack-ruby-without-assets-precompile,andycroll/heroku-buildpack-jekyll,tpope/heroku-buildpack-ruby-tpope,andycroll/heroku-buildpack-jekyll,mattmanning/heroku-buildpack-ruby-jekyll,jumptvs/BP_Ruby,vhx/heroku-buildpack,pilotcreative/heroku-buildpack-ruby,cloudfoundry/ruby-buildpack,Scalingo/ruby-buildpack,ekaranto/rails4-bluemix-buildpack,Scalingo/ruby-buildpack,zunda/heroku-buildpack-ruby,beydogan/ruby-buildpack,mattmanning/heroku-buildpack-ruby-jekyll,zoomer/heroku-buildpack-ruby-bower,instacart/heroku-buildpack-ruby,tenjikinc/heroku-buildpack-ruby,makifund/heroku-buildpack-ruby,markaschneider/heroku-buildpack-ruby-ffmpeg-sox,vhx/heroku-buildpack,orenyk/heroku-buildpack-ruby,instacart/heroku-buildpack-ruby,ruby/heroku-buildpack-www-ruby-lang,makifund/heroku-buildpack-ruby,pkgr/heroku-buildpack-ruby,zunda/heroku-buildpack-ruby,jumptvs/BP_Ruby,qnyp/heroku-buildpack-ruby-bower,Genius/heroku-buildpack-ruby