add linum-plus

.gitmodules

@@ -0,0 +1,3 @@
+[submodule "lib/linum-plus"]
+	path = lib/linum-plus
+	url = https://github.com/emacsmirror/linum-plus

lib/linum-plus

@@ -0,0 +1 @@
+Subproject commit 2fa258b437e495602c5f737819046414294ea8cb