Python 3 Support

[ironmaniiith]

The code is not compatible with python 3, if you are willing to accept PRs I would love to contribute to it 😄

[andreasveit]

This sounds like a good suggestion. We welcome you to send a PR. Thanks!

[saifhassan]

In coco_evaluation, error occurs in decode function: Bytes-Like object is required not str. Python 3 does not support.