fix(heroku): Changed port variable to capital letters so heroku recognize it

Heroku uses process.env.PORT with capital letters.

closes #2185

Author: amygdaloideum

Diff for: templates/app/server/config/environment/production.js

@@ -11,7 +11,7 @@ module.exports = {
 
   // Server port
   port: process.env.OPENSHIFT_NODEJS_PORT
-    || process.env.port
+    || process.env.PORT
     || <%= prodPort %><% if(filters.mongoose) { %>,
 
   // MongoDB connection options