Refactored code to improve performance
 # What does this PR do?
 Refactors several segments of code in the `scripts`,`src`,`tests`,`utils` and `setup.py` and increases performance by a bit, using compression methods and newer practices.
 
 No new functions or methods/models were added; therefore no documentation changes were required.
 
 ## Before submitting
 * [ ]  This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
 * [x]  Did you read the [contributor guideline](https://github.com/huggingface/transformers/blob/master/CONTRIBUTING.md#start-contributing-pull-requests),
   Pull Request section?
 * [ ]  Was this discussed/approved via a Github issue or the [forum](https://discuss.huggingface.co/)? Please add a link
   to it if that's the case.
 * [ ]  Did you make sure to update the documentation with your changes? Here are the
   [documentation guidelines](https://github.com/huggingface/transformers/tree/master/docs), and
   [here are tips on formatting docstrings](https://github.com/huggingface/transformers/tree/master/docs#writing-source-documentation).
 * [ ]  Did you write any new necessary tests?

