Update README.rst

The example in readme cannot work now, have to use 'GOOGL' after the split in January. GOOG only stands for C share, and yahoo.com does not have historical information of 'GOOG' anymore, use 'GOOGL' instead.

still other queries for 'GOOG' works NOW.(but only till June 20,2014 I believe, then NASDAQ-100 will remove 'GOOG' and use 'GOOGL' after then)

README.rst

@@ -42,17 +42,17 @@ Example Usage
 .. code:: python
 
     >>> import ystockquote
-    >>> print(ystockquote.get_price_book('GOOG'))
+    >>> print(ystockquote.get_price_book('GOOGL'))
     '51.18'
-    >>> print(ystockquote.get_bid_realtime('GOOG'))
+    >>> print(ystockquote.get_bid_realtime('GOOGL'))
     '904.77'
     >>>
 
 .. code:: python
 
     >>> import ystockquote
     >>> from pprint import pprint
-    >>> pprint(ystockquote.get_historical_prices('GOOG', '2013-01-03', '2013-01-08'))
+    >>> pprint(ystockquote.get_historical_prices('GOOGL', '2013-01-03', '2013-01-08'))
     {'2013-01-03': {'Adj Close': '723.67',
                     'Close': '723.67',
                     'High': '731.93',