Allow string coordinates in rolling window. Closes #1108.
Increased git depth to 10000
Added explicit Python path to grib-api configure
Merge pull request #1113 from dkillick/travis_git_depth

Increased git depth to 10000 and specified python binary for grib
Made matplotlib an optional iris tests dependency
Merge pull request #1109 from dkillick/no_graphics_tests

Make matplotlib an optional Iris tests dependency
Merge pull request #1110 from ajdawson/rolling-window-string

Allow string coordinates in rolling window
Added mdtol kwarg to area weighted regridding