Tasks for 2.0 release

[nielsenmb]

This is a to-do list to prepare for the release of 2.0.

• Unit tests
• Trim down the time series ingestion bit in IO.py, the lk.searchresult caching is no longer necessary since LK is fast enough now.
• Make sure the rotation and inclination output from peakbag is handled neatly with and without slicing.
• Tutorials need to be updated to show examples of the session and star classes and more advanced tutorials on using the modeID, peakbag in a bit more detail.
• Readthedocs needs to be updated.
• PyPi needs to be updated
• Update Readme to reflect PBjam 2.0
• Update Contributing with instructions
• Update Contributors

Post release ideas:

• in select_n_g we could swap out Dynesty with emcee, probably a bit faster.
• Build in a better prior for rotation. modeID currently uses $\nu_{rot}$ directly as the splitting, while peakbag uses $\nu_{rot} \sin(i)$. This should probably be more consistently done, and with a meaningful prior implemented. At the moment we're just using uniform priors.