Mwahpy

- can now search by ID in timestep.print_particle() with use_id=True keyword
- timestep.subset_rect() and timestep_subset_circ() now both have an inverse=True keyword,
which lets you cut everything inside the bounds instead of keeping everything inside bounds
- removed extra unecessary .update()s in timestep.subset_rect(), timestep.subset_circ(),
timestep.split(), timestep.split_at_id_wrap(), and recenter_each_component()
- added histogram reading capability in output_handler.read_histogram()

- fixed bug in computing vgsr and vr for simulated data
- corrected rotation matrix and typo in coords.eq_to_OC_koposov2019()
- added inverse coords.OC_to_eq_koposov2019()
- added fix_arrays decorator to coords that makes it a lot easier to implement flexible
array & non-array inputs
- added some flexible array/non-array inputs to various coords functions

- made the goodness-of-fit in orbit_fitter an actual chi-squared
- fixed type mismatch in coords.pole_rotation_inv
- added timestep.get_bound_mass()
- added timestep.check_for_incest()
- edited github readme
- split_at_id_wrap works again for new Nbody formatting, added a toggle for user-inputted
values for backwards compatability
- added plot.scatter_multiple() to plot lists of timesteps (like those made by split_at_id_wrap)
- added a few paper&stream-specific transformations (gal_to_lambet_newberg2010(),
lambet_to_gal_newberg2010(), and eq_to_OC_koposov2019())

- the reverse orbit in orbit_fitter.get_OrbitData_from_orbit() was using the forwards
orbit to calculate vgsr. Fixed
- timestep.only_dark_matter() had a typo that made it identical to only_baryons(). Fixed
- did some refactoring of orbit_fitter to make it easier to read and more consistent with
things like changing the timestep and potential

- fixed bug where orbit fitter plots would use the mwahpy default potential even
if another was provided
- output_handler.read_output() now works for files with the <bodies> </bodies> tags format
- changed name of sky_to_pole() to pole_rotation(), because it was confusing.
sky_to_pole() is now an alias for pole_rotation() and causes a DeprecationWarning
- added pole_rotation_inv() function
- timestep.scatter() now has a 'cbar' keyword to turn on a colorbar & shade particles appropriately
- improved how .coords was checking types
- added eq_to_OC() transformation from ra/dec to Orphan-Chenab lambda/beta,
and OC_to_eq() inverse transformation

- orbit_fitter gradient descent now uses Nelder-Mead optimizer by default, BFGS
was terminating the optimization early
- fixed bug in calc_self_energies where KE was 2x as large as it should be
- added ability to change galaxy potential in orbit_fitter.py