added commands in dockerfile to install git

[arvy-p]

Issue #, if available:

Description of changes:
I have updated Dockerfile with RUN commands to have git installed

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[fjpa121197]

One question regarding this.

Should git be installed before the following command?

RUN pip install papermill jupyter nteract-scrapbook boto3 requests && pip install -r /tmp/requirements.txt

In case there are git commands in requirements.txt

[tomfaulhaber]

Sorry, I'm getting to this late.

What is the motivation for having git in the default container? Is it a requirement for a common use case here? At container build time or container run time?