reformat URL attributes

these were using :var: which seems to not work now,
not sure if this broke due to sphinx 1.4 or if this was
broken anyway, but these are not even refs that can be picked
up by zzzeeksphinx now.

Change-Id: I24ae968ae5d870ec949b2b07dbad2afa6969a189

lib/sqlalchemy/engine/url.py

@@ -72,17 +72,17 @@ class URL(
 
     :class:`_engine.URL` contains the following attributes:
 
-    :var `_engine.URL.drivername`: database backend and driver name, such as
-     ``postgresql+psycopg2``
-    :var `_engine.URL.username`: username string
-    :var `_engine.URL.password`: password, which is normally a string but may
-     also be any object that has a ``__str__()`` method.
-    :var `_engine.URL.host`: string hostname
-    :var `_engine.URL.port`: integer port number
-    :var `_engine.URL.database`: string database name
-    :var `_engine.URL.query`: an immutable mapping representing the query
-     string.  contains strings for keys and either strings or tuples of strings
-     for values.
+    * :attr:`_engine.URL.drivername`: database backend and driver name, such as
+      ``postgresql+psycopg2``
+    * :attr:`_engine.URL.username`: username string
+    * :attr:`_engine.URL.password`: password, which is normally a string but
+      may also be any object that has a ``__str__()`` method.
+    * :attr:`_engine.URL.host`: string hostname
+    * :attr:`_engine.URL.port`: integer port number
+    * :attr:`_engine.URL.database`: string database name
+    * :attr:`_engine.URL.query`: an immutable mapping representing the query
+      string.  contains strings for keys and either strings or tuples of
+      strings for values.
 
 
     """