Change encoder-decoder option parameter for an offset parameter

This way, the offset can be adjusted directly in the call, and saves
time adjusting the offset in the code.

Also, it allows the tfglib code to work with less changes and commits

tfglib/utils.py

@@ -111,7 +111,7 @@ def display_time(seconds, granularity=2):
     return ', '.join([x for x in result[:granularity] if x is not None])
 
 
-def s2s_load_weights(model, filepath, mode):
+def s2s_load_weights(model, filepath, offset=0):
     import h5py
     from keras import backend as K
     w_file = h5py.File(filepath, mode='r')
@@ -147,17 +147,6 @@ def s2s_load_weights(model, filepath, mode):
                 filtered_layers.append(layer)
                 indexes.append(index)
 
-        if mode is 'encoder':
-            offset = 0
-
-        elif mode is 'decoder':
-            # offset = 6
-            offset = 5
-
-        else:
-            raise Exception("Unrecognized mode. Please choose 'encoder' or" +
-                            " 'decoder' as a mode")
-
         indexes = [index + offset for index in indexes]
         flattened_layers = filtered_layers