dependencies: Start using pipenv for dependency management
    
    This commit adds a Pipfile with some of the dependencies Fedora
    Happiness Packets uses. See more about pipenv here:
    
        https://fedoramagazine.org/install-pipenv-fedora/
    
    I am making this change to help us migrate to a single set of
    dependencies. Currently, there are multiple sets of dependencies for
    development, production, and the CI environment. The issue with this is
    we could have different versions of software at the same time. For
    example, a passing build in a CI environment might not work in
    production or vice versa.
    
    Ultimately, we should strive to use a single set of dependencies across
    the project. pipenv adds a nice front-end to managing dependencies and
    helps us manage them at the top-level of the project. For now, this is
    just a start but we should work on migrating the requirements here over
    time.