[Tree] Materialized Path: Added some more documentation

README.md

@@ -97,6 +97,7 @@ List of extensions which support ODM
 - Timestampable
 - Loggable
 - Translator
+- Tree (Materialized Path strategy for now)
 
 All these extensions can be nested together and mapped in traditional ways - annotations,
 xml or yaml

doc/tree.md

@@ -988,7 +988,7 @@ $fruits->setParent($food);
 $em->persist($fruits);
 $em->flush();
 
-// This would print "Food-1,Fruits-2" assuming that $food id is 1, $fruits id is 2 and separator = "|" (the default value)
+// This would print "Food-1,Fruits-2" assuming that $food id is 1, $fruits id is 2 and separator = "," (the default value)
 echo $fruits->getPath();
 
 ```