Esmvaltool

This release includes all the work done in the past year.

Major milestones:

- More than 50 recipes are now available, including all diagnostics for the MAGIC project
- In addition to diagnostic scripts in Python and NCL, diagnostics in R and Julia are now also supported
- Provenance information can now be collected and many recipes already use this feature
- Support for more models (CMIP5 and CMIP6) and observational datasets
- Various new preprocessor functions
- Improved reliability
- Contribution guidelines in CONTRIBUTING.md
- More documentation on [readthedocs](http://esmvaltool.readthedocs.io)
- Upgraded to Iris 2
- Dropped support for Python 2

This release includes much of the work done at the recent DLR workshop.

Major milestones:
- We now have eight real recipes (formerly known as namelists) in addition to several example recipes, available in the new version.
- New preprocessor functions for masking by threshold and land/sea.
- New recipe functionality for reading fx-variables

Preview of the upcoming version 2 release.