Update of CITATION cff and RELEASE

CITATION.cff

@@ -50,7 +50,7 @@ authors:
     given-names: Arnold
     orcid: "https://orcid.org/0000-0003-1711-7961"
 cff-version: "1.0.3"
-date-released: 2018-03-08
+date-released: 2019-06-13
 doi: "10.5281/zenodo.597993"
 keywords: 
   - Java
@@ -69,6 +69,6 @@ keywords:
   - "distributed computing"
 license: Apache-2.0
 message: "If you use this software, please cite it using these metadata."
-repository-code: "https://github.com/NLeSC/Xenon"
+repository-code: "https://github.com/xenon-middleware/xenon"
 title: Xenon
-version: "2.6.0"
+version: "3.0.0"

RELEASE.md

@@ -23,6 +23,13 @@ To update Xenon version in `docs/_data/version.yml` and update Javadocs inside `
 
 The site is a [Jekyll](https://jekyllrb.com/) powered site and hosted by GitHub pages at http://nlesc.github.io/Xenon/
 
+## 2.1 Update the CITATION.cff
+
+The CITATION.cff contains the information on how to cite xenon in scientific applications. Update the authors list is needed, and
+change the date-released and version fields to reflect the current release.  
+
+NOTE: the CITATION.cff contains the concept DOI of xenon (refering to all versions), so this does not need to be changed. 
+
 ## 3. Commit the changes
 
 Next, commit all changes you have made to the master branch. If you check with