Enable output padding (#31)

* allow output padding

* avoid non writeable np array warning

* re-remove np.copy

Author: c3-andyehrenberg

onnx2pytorch/convert/attribute.py

@@ -223,6 +223,8 @@ def extract_attributes(node):
             kwargs["constant"] = extract_attr_values(attr)
         elif attr.name == "value_strings":
             kwargs["constant"] = extract_attr_values(attr)
+        elif attr.name == "output_padding":
+            kwargs["output_padding"] = extract_attr_values(attr)
         elif node.op_type == "Resize":
             # These parameters are not used, warn in Resize operator
             kwargs[attr.name] = extract_attr_values(attr)