Add an optimisation for single valued coordinate constraints.
Fix to license check logic
Updates to erroneous copyright years based on git history.
Merge pull request #487 from esc24/licence_fix

Fix to copyright licence check logic.
fixed netcdf save cubelist bug
Cope with non-numeric/Cell values.
Area weighted regridding.
Merge pull request #488 from cpelley/fix_netcdfsavebug

Fixed NetCDF saving of special case of CubeList.
Update licence dates.
Merge pull request #428 from rhattersley/constraint-speed

Add an optimisation for single valued coordinate constraints.
Update categorical coordinate names to match function names.
Warn on deprecated defaults and deprecate the aliased functions.
Merge pull request #480 from rhattersley/unambiguous_season_year_naming

Unambiguous season year naming
Review actions.
Refactor seasons categorisation functions.

Deprecates the add_custom_season* functions in favour of adding their
functionality to the existing season categorisation functions via a
keyword argument.
PEP8 corrections to iterate.py.
Merge pull request #464 from esc24/area_weighted_regrid

Area weighted regridding
Merge pull request #491 from esc24/iterate_pep8

PEP8 corrections to iterate.py.
Removal of strict constraint in izip().
Merge pull request #490 from ajdawson/refactor-seasons-categorisation

Refactor seasons categorisation functions.