Add Pipfile to use on circleci

[fortin-alex]

User story
As a developer working on this repo,
I want my tests and checks to be compatible with circleci,
So that I can only merge good quality code.

At the moment, pipenv does not support specifiying different package version based on OS or platform. So we will maintain 2 Pipfile. One that uses the raspberry pi specific versions of torch, and torchvision and another one that uses the regular versions of the same package version.

See pipenv discussion on this issue here.

Acceptance criteria

• Add Pipfile and Pipfile.lock in ./.circleci
• Modify ./circleci/config.yaml to use the circleci specific environment