[semver:minor] Compatibility fixes and LGPL license

As with psyplot 1.4.0, psyplot-gui is now continuously tested and deployed with CircleCI.

Added
-----
-   psyplot-gui does now have a CITATION.cff file, see https://citation-file-format.github.io

Changed
-------
-   psyplot is now officially licensed under LGPL-3.0-only, see [#29](https://github.com/psyplot/psyplot/pull/29)
-   Documentation is now hosted with Github Pages at https://psyplot.github.io/psyplot-gui. Redirects from the old documentation at [https://psyplot-gui.readthedocs.io]{.title-ref} have been configured.
-   We use CicleCI now for a standardized CI/CD pipeline to build and test the code and docs all at one place, see [#28](https://github.com/psyplot/psyplot-gui/pull/28)

.circleci/config.yml

 version: 2.1
 
 orbs:
-  psyplot: psyplot/psyplot-ci-orb@1.5.24
+  psyplot: psyplot/psyplot-ci-orb@1.5.25
   mattermost-plugin-notify: nathanaelhoun/mattermost-plugin-notify@1.2.0
 
 executors:
@@ -38,7 +38,7 @@ workflows:
           build_docs: << pipeline.parameters.build_docs >>
       - psyplot/test-parallel:
           name: run-tests
-          parallelism: 2
+          parallelism: 1
           pytest_args: --cov=psyplot_gui
           run-job: << pipeline.parameters.run-tests >>
           requires:

CHANGELOG.rst

@@ -6,6 +6,11 @@ As with psyplot 1.4.0, psyplot-gui is now continuously tested and deployed with
 CircleCI.
 
 
+Added
+-----
+- psyplot-gui does now have a CITATION.cff file, see https://citation-file-format.github.io
+
+
 Changed
 -------
 - psyplot is now officially licensed under LGPL-3.0-only,