Added link to blog post (#662)

Summary:
Added link to blog post about incremental decoder in the FairseqIncrementalDecoder class description.
Pull Request resolved: https://github.com/pytorch/fairseq/pull/662

Differential Revision: D15077845

Pulled By: myleott

fbshipit-source-id: f23294721739600e14feb2cca4ece95f2b968f44

fairseq/models/fairseq_incremental_decoder.py

@@ -25,6 +25,9 @@ class FairseqIncrementalDecoder(FairseqDecoder):
     The :class:`FairseqIncrementalDecoder` interface also defines the
     :func:`reorder_incremental_state` method, which is used during beam search
     to select and reorder the incremental state based on the selection of beams.
+	
+    To learn more about how incremental decoding works, refer to `this blog
+    <http://www.telesens.co/2019/04/21/understanding-incremental-decoding-in-fairseq/>`_.
     """
 
     def __init__(self, dictionary):