v1.3.4:
 - Timestep.typ attribute stores whether particles are baryons (0) or dark matter (1)
 - output_handler has been updated to also read in particle type
 - Timestep.only_baryons() and Timestep_only_dark_matter() cut the data to only
   include one type of particle
 - Added support for galactic spherical coordinates (phi, theta)
 - Added find_progenitor()
 - make_nbody_input() no longer recenters the Timestep before printing out
 - fixed 'self not defined' error in output_handler.make_csv()
 - Timestep.rad and Timestep.rot are now Timestep.vrad and Timestep.vrot
 - updated documentation pdf to new naming convention
 - updated documentation to include all supported functions
 - updated README
 - removed coords.approx_lsr()

v1.3.3:
 - added changelog
 - fixed bug in Timestep.copy() that would cause error if the Timestep had calculated values
 - adapted python standard naming convention (mostly, method names went from camelCase to lower_case)
 - consolidated coords.py tests into tests.py
 - bug fix in coords.cart_to_plane()
 - fixed import scheme
