Release 1.4.0

[rhpvorderman]

Release checklist

• Check outstanding issues on JIRA and Github.
• Check latest documentation looks fine.
• Create a release branch.
  • Set version to a stable number.
  • Change current development version in HISTORY.rst to stable version.
• Merge the release branch into master.
• Create a test pypi package from the master branch. (Instructions.)
• Install the packages from the test pypi repository to see if they work.
• Created an annotated tag with the stable version number. Include changes
  from history.rst.
• Push tag to remote.
• Push tested packages to pypi.
• merge master branch back into develop.
• Add updated version number to develop.
• Build the new tag on readthedocs. Only build the last patch version of
  each minor version. So 1.1.1 and 1.2.0 but not 1.1.0, 1.1.1 and 1.2.0.
• Create a new release on github.
• Update the package on conda-forge.