Clarify README on pgspecial commands

Author: catherinedevlin

NEWS.txt

@@ -148,3 +148,4 @@ Deleted Plugin import left behind in 0.2.2
 * `<<` operator (thanks xiaochuanyu)
 * added README example (thanks tanhuil)
 * bugfix in executing column_local_vars (thanks tebeka)
+* pgspecial installation optional (thanks jstoebel and arjoe)

README.rst

@@ -265,7 +265,11 @@ PostgreSQL features
 -------------------
 
 ``psql``-style "backslash" `meta-commands`_ commands (``\d``, ``\dt``, etc.)
-are provided by `PGSpecial`_.
+are provided by `PGSpecial`_.  Example:
+
+.. code-block:: python
+
+    In[9]: %sql \d
 
 .. _PGSpecial: https://pypi.python.org/pypi/pgspecial