Add information about pytorch-02 branch

Author: hassony2

README.md

@@ -14,6 +14,13 @@ To generate the flow weights, use `python i3d_tf_to_pt.py --flow`.
 
 You can also generate both in one run by using both flags simultaneously `python i3d_tf_to_pt.py --rgb --flow`.
 
+Note that the master version requires PyTorch compiled from master because it relies the recent addition of ConstantPad3d in the torch source code.
+
+If you want to use pytorch 0.2 checkout the branch pytorch-02 which contains a simplified model with even padding on all sides (and the pytorch weight checkpoints).
+The difference is that the 'SAME' option for padding in tensorflow allows it to pad unevenly both sides of a dimension, an effect reproduced on the master branch.
+
+This simpler model produces scores a bit closer to the original tensorflow model on the demo sample and is also a bit faster.
+
 ## Demo
 
 There is a slight drift in the weights that impacts the predictions, however, it seems to only marginally affect the final predictions, and therefore, the converted weights should serve as a valid initialization for further finetuning.