Update Tensorflow version to 2.1 and Python3

[sergiopaniego]

Tensorflow 2.1 is the current stable version of tf.
Since we have some functionality in tf, it would be a good idea to update the current version of tf.
Additionally, since Python 2.7 is no longer maintained, update it to Python 3.x

[hmrishavbandy]

Hi, I would like to work on this. This requires me to just remove and replace the obsolete features in python 2.7 and Tensorflow right?

[hmrishavbandy]

I have updated to python3.6.9 and will submit the pull request to the same. I hope it is alright to solve this part by part.

[sergiopaniego]

You can submit two pull request, one for each problem.

[hmrishavbandy]

Yes, but i have actually not created a branch from master in my fork of the project before committing and now i cant commit before the pull request is merged :(