Merge pull request #775 from progrium/plugin-help

Add PLUGIN:help command to each plugin

plugins/nginx-vhosts/commands

@@ -34,7 +34,7 @@ case "$1" in
     mv "$TEMP_DIR/server.key" "$DOKKU_ROOT/$APP/tls/server.key"
     rm -rf $TEMP_DIR
     ;;
-  help)
+  help | nginx:help)
     cat  && cat<<EOF
     nginx:import-ssl <app>                          Imports a tarball from stdin; should contain server.crt and server.key
 EOF