more nbs for docs

[jrob93]

Fixes #168.

Adding additional notebooks to read the docs to cover plotting, outlier detection and colour measurement.

Review Checklist for Source Code Changes

• Does pip install still work?
• Have you written a unit test for any new functions?
• Do all the units tests run successfully?
• Does adler run successfully on a test set of input files/databases?
• Have you used black on the files you have updated to confirm python programming style guide enforcement?

[jrob93]

Here's some more notebooks for the read the docs. I had a bit of trouble with nb section headers and rendering the readthedocs toc; I've added a tips to the lsst-adler/README.md.