Added a bit of covid data and analysis notebook

Added Oura API code starters

Added sample ics file and sample notebook for importing calendar events and external correlations.

Cleaned up README a bit

Added Oura correlations sample notebook

Minor adjustments

Minor fixes

Improved indexing a bit, added weekdays, and added more values to plot

Using matplotlib directly vs via dataframe to have more access to the plot

Initial import. Got the data, got a notebook.