data don't ship with the package

[CommonClimate]

Describe the bug
https://pyleoclim-util.readthedocs.io/en/latest/core/api.html#pyleoclim.core.multipleseries.MultipleSeries

** Solution**
create a data folder under pyleoclim/ and put ONLY the load_dataset() csv files in there. LiPD files will be accessed via pyLipd and the graphdb. Details:

• https://kiwidamien.github.io/making-a-python-package-vi-including-data-files.html
• https://sixty-north.com/blog/including-package-data-in-python-packages.html
• test on RTD

[CommonClimate]

csv files are now included. the fate of LiPD files will be decided at the Team Hackathon in May.

[CommonClimate]

load_dataset() now works in the doc, so we can close.