Add asl module lib

[BenoitDherin]

This PR adds the folder asl at the top level directory to hold our code utils (e.g., convenients wrappers around GCP API calls). For now, it contains only a single file lib.py with two functions:

• upload_directory_to_gcs that upload a local folder to a bucket
• download_directory_from_gcs that download the content of a bucket path to a local folder

The setup has been modified (Makefile, requirements.txt, plus an additional setup.py) so that now make install has for result that the asl module can be imported directly in any notebook after make install is ran. If the code in the ./asl folder is modified, there should not be a need for re-runing make isntall (because of the pip install -e . in the Makefile). Here is an example how to import the asl module in the notebook:

A test folder named tests has been added as placeholder for the unit tests for the asl module. Now make tests triggers the tests.

[takumiohym]

@BenoitDherin That's a nice idea to add lib for reusable small util functions.

In terms of the functions you added, could you share more context on when we use them?
For directory copy, I usually use gsutil cp -r simply and haven't met situations where it is not enough.

[sanjanalreddy]

@BenoitDherin the PR is failing the pre-commit, except for that the code looks good to me! Once the pre-commit check passes, you can merge.

[takumiohym]

pre-commit failure is fixed in this PR. #454
If you want to confirm, you can rebasing on the current master branch. (Or you can just ignore the error.)