Change stopnginx alias to run sudo nginx -s stop

stopnginx now stops nginx gracefully instead of just killing the process.

packages/nginx.rb

@@ -20,6 +20,6 @@ class Nginx < Package
     system "echo adding bash aliases so you can easily start/stop nginx"
     system "echo startnginx starts nginx and stopnginx stops nginx"
     system "sed -i '$ a alias startnginx=\"sudo nginx\"' ~/.bashrc"
-    system "sed -i '$ a alias stopnginx=\"sudo pkill nginx\"' ~/.bashrc"
+    system "sed -i '$ a alias stopnginx=\"sudo nginx -s quit\"' ~/.bashrc"
   end
 end