Update MongoDB Manual link for mapreduce command.

Author: ajdavis

pymongo/collection.py

@@ -1671,7 +1671,7 @@ def map_reduce(self, map, reduce, out, full_response=False, **kwargs):
  .. versionchanged:: 2.2
  Removed deprecated arguments: merge_output and reduce_output
 
- .. _map reduce command: http://www.mongodb.org/display/DOCS/MapReduce
+ .. _map reduce command: http://docs.mongodb.org/manual/reference/command/mapReduce/
 
  .. mongodoc:: mapreduce
  """