Updated the master version.
Merge remote-tracking branch 'upstream/v1.5.x'
Merge remote branch 'upstream/v1.5.x'

* upstream/v1.5.x:
  Added example to iris.analysis.interpolate.linear docstring
  Bugfix to DimCoord.from_regular
  Change zorder of contour lines drawn by contourf.
  Modified cube dim_coords and aux_coords docstrings
  Simplified ionosphere example. Closes #603.
  Use space_weather.nc instead of missing file and enabled doctests
Added support for UM fieldsfile ancillary files trunkated with ieee.
Add netCDF export support for transverse Mercator.
Handle directory creation race condition.
Added flexibilty when saving integer types to netCDF3
Merge pull request #742 from rhattersley/transverse-merc-to-nc

Add netCDF export support for transverse Mercator.
Merge pull request #743 from rhattersley/makedirs-race-fix

Handle directory creation race condition.
Ensure consistent memory layout for checksums.
Merge pull request #740 from pelson/ancillary_ieee_32

Added the magic lines to support UM ancillary files trunkated with the UM utility ieee.
Merge pull request #731 from rhattersley/normalise_checksum_data

Ensure consistent memory layout for checksums.
Corrected 'temperature' var name to 'air_pressure', plus a couple of PEP8 changes
Merge remote branch 'upstream/v1.5.x'

* upstream/v1.5.x:
  Handle directory creation race condition.
  Add netCDF export support for transverse Mercator.
  Added support for UM fieldsfile ancillary files trunkated with ieee.
Merge remote branch 'upstream/master'

* upstream/master:
  Ensure consistent memory layout for checksums.
Respect major/minor axes when converting to Cartopy.
Merge pull request #748 from rhattersley/fix-geogcs

Respect major/minor axes when converting GeogCS to Cartopy.
BUG: Fixed typo in OSGB.
Refactor common code and fix for PEP8 1.4.6.
Support for projection_origin and central_meridian