Updated version numbers to be X.Y.Z for full semantic versioning.
Added bumpversion config file.
Bumped to v1.3.1
Added first go of parallelising multiple wavelength running.

Uses threading from multiprocessing.dummy, and currently implemented as
a separate function within all_wavelengths.py, for testing.
Added n= option to set number of threads
Replaced run_wavelengths with the parallel version

Also updated all functions to pass keyword arguments through, making them simpler and more extensible.
Removed all old commented out centre wavelengths
Added __version__ attribute to SixS, plus updated BumpVersion config to update this.
Updated run360 to use parallelisation in the same way as run_wavelengths.
Fixed error in run_and_plot_360 docstring.
Updated run_principal_plane to run in parallel too.
Moved all multiprocessing imports to the top
Added produce_debug_report function
Updated angle running routines to return arrays for all outputs.
Added test for run360 and moved helper tests to separate file.
Changed results of running for multiple angles to all be arrays
Updated multi-wavelength test to specify output_name keyword
Added test for run_vnir
Updated LandsatETM wavelength test to use np.testing.assert_allclose
Updated run_vnir test to use 100 wavelengths