Introduce URL for app. Plugins can override this.

fixes #242

plugins/nginx-vhosts/commands

@@ -1,18 +1,2 @@
 #!/bin/bash
-set -e; case "$1" in
-
-  url)
-    if [[ -f "/home/git/$2/VHOST" ]]; then
-      echo "http://$(< "/home/git/$2/VHOST")"
-    else
-      cat
-    fi
-    ;;
-
-  help) cat && cat<<EOF
-    url <app>                                       Show the URL for an application
-EOF
-    ;;
-
-esac
 cat