* Use regular dicts for sleep pattern (WIP)
* Remove dataframes code from sleep pattern graph
* Reimplement UTC offset change handling
* Move label formatting in to a function
* Remove pandas!
* Fix linting issue
* Add dev requirements to generated requirements.txt
* Stop committing Pipfile.lock
Pipenv is designed to pin to a specific version of Python. Including the lock
file can lead to failed builds or broken package configurations on different
system architectures and/or Python versions.