Add submodule support to kiss.

Simple pr that adds support for submodules basically adds no time to repos that dont have submodules as far as I can tell.

kiss

@@ -259,6 +259,7 @@ pkg_extract() {
                     git remote add origin "${url%[#@]*}"
                     git fetch --depth=1 origin "$com" || git fetch
                     git checkout "${com:-FETCH_HEAD}"
+                    git submodule update --init --recursive
                 } || die "$1" "Failed to clone $src"
             ;;