Version 2.8.0

Version 2.7.0

Version 2.6.1

Version 2.6.0

Version 2.5.0

Version 2.4.0

don't package doc/deposition in release tarball

fix typeface for aero_mass_concentration in ChangeLog

add docs for aero_state_scale_comp_vol()

update info for 2.1.5 release