new CubeList method to extract over common coord values
Changed to generator comprehension
Default NetCDF dimensionless unit.
Concatenate with scalar coordinate.
Review actions.
progress
Fix string formatting bugs in STASH object error messages.
Add pp constraint conversion test where STASH=stash-object (instead of string).
Allow STASH-constraint conversion where reference is a STASH object (instead of a string).
Removed patch awareness from test
new metarelate api
Hide new API.

Change from:
    iris.fileformats.grib.GribMessage
to:
    iris.fileformats.grib.message._GribMessage.
Use both _GribMessage() and _RawGribMessage().
Added likely location of test images to git ignore file.
Merge pull request #1314 from ajdawson/image-output-location

Added likely location of test images to git ignore file.
Watch out for scanning mode
Merge pull request #1313 from rhattersley/grib-data

Fix new GRIB data interpretation
Switch to simultaneous conda install.
Merge pull request #1316 from rhattersley/test-fix

Switch to simultaneous conda install.
Allow users to choose the number of processors used for running tests.