RFC: CmpStatus command (#210)

* Add `CmpStatus` command

* Update headings

* Fix heading

* Update headings

* Add README.md

* Fix tests

* Force invoke InsertEnter

lua/cmp/config.lua

@@ -65,7 +65,7 @@ config.get_source_config = function(name)
         return s
       end
     end
-    return {}
+    return nil
   end)
 end