Use Pipenv for Dependency Management

[idodin]

Currently, no dependency management exists for this project.

Using a requirements.txt file (e.g. pip dependency management) is an option, but it is preferable to use Pipenv instead. The latter will automatically create a virtual environment to run the project in and installs the dependencies into this virtual environment. More details can be found here.

[idodin]

Note that the install_requires keyword in the setup.py file discussed in #4 must additionally outline the minimal dependencies for the project. Allowing users to install these dependencies via pipenv is still nice, particularly in the case of contributors.