Better formatting and make clear this is a note to users

Author: robertfeldt

README.md

@@ -162,7 +162,7 @@ add_text(xs3, "California")
 set_attributes(xs3; tag="CA", cap="Sacramento")
 ```
 
-Please note that when you create XML documents and elements directly you need to take care not to leak memory; memory management in the underlying libxml2 library is complex and LightXML currently does not integrate well with Julia's garbage collection system. You can call free on an XMLDocument but if you are directly creating XMLElement's there is not yet a corresponding free function to call.
+**Note:** When you create XML documents and elements directly you need to take care not to leak memory; memory management in the underlying libxml2 library is complex and LightXML currently does not integrate well with Julia's garbage collection system. You can call ``free`` on an XMLDocument but if you are directly creating XMLElement's there is not yet a corresponding ``free`` function to call.
 
 #### Export an XML file