Move ids poster to posterdown_ids and restore original posterdown_html

Change-Id: Ib44b4020134c403a2946d0fc4b79777e9ecbe3ac
diff --git a/NAMESPACE b/NAMESPACE
index bf49ea6..2d0979e 100644
--- a/NAMESPACE
+++ b/NAMESPACE
@@ -3,3 +3,4 @@
 export(posterdown_betterland)
 export(posterdown_betterport)
 export(posterdown_html)
+export(posterdown_ids)