doc: Fix incorrect example for req.get_param() in README.md

As of version 0.1.4, req.get_param() no longer accepts a "default"
parameter. Instead, callers are encourage to use the idiomatic
python "or" pattern. For example:

limit = req.get_param('limit') or 10

Fixes #132

README.md

@@ -134,8 +134,8 @@ class ThingsResource:
         self.logger = logging.getLogger('thingsapi.' + __name__)
 
     def on_get(self, req, resp, user_id):
-        marker = req.get_param('marker', default='')
-        limit = req.get_param_as_int('limit', default=50)
+        marker = req.get_param('marker') or ''
+        limit = req.get_param_as_int('limit') or 50
 
         try:
             result = self.db.get_things(marker, limit)

falcon/request.py

@@ -412,8 +412,8 @@ class Request(object):
 
         Returns:
             The value of the param if it is found and can be converted to an
-            integer. If the param is not found, returns None, unless
-            unless required is True.
+            integer. If the param is not found, returns None, unless required
+            is True.
 
         Raises
             HTTPBadRequest: The param was not found in the request, even though