PEP 8 iris.unit
Merge pull request #799 from rhattersley/pep8-iris.unit

PEP 8 iris.unit
PEP8 iris.coord_systems
Merge pull request #797 from rhattersley/pep8-iris.coord_systems

PEP8 iris.coord_systems
Remove old deprecations.
Merge pull request #800 from rhattersley/deprecations

Remove old deprecations.
Move netCDF4 and pyke to optional installs
Move scipy to optional installs