Update readme.md for new version 2019.2

Author: Sebastian Hönel

readme.md

@@ -47,11 +47,12 @@ ___
 Please use the following BibTeX to cite __`GitDensity`__:
 <pre>
 @article{honel2019gitdensity,
-  title={Git Density (2019.1): Analyze git repositories to extract the Source Code Density and other Commit Properties},
-  DOI={10.5281/zenodo.2565239},
-  url={http://doi.org/10.5281/zenodo.2565239},
+  title={Git Density: Analyze git repositories to extract the Source Code Density and other Commit Properties},
+  DOI={10.5281/zenodo.2574611},
+  url={http://doi.org/10.5281/zenodo.2574611},
   publisher={Zenodo},
   author={Sebastian Hönel},
+  version={2019.2}
   year={2019},
   month={Feb},
   abstractNote={Git Density (<code>git-density</code>) is a tool to analyze <code>git</code>-repositories with the goal of detecting the source code density. It was developed during the research phase of the short technical paper and poster &quot;<em>A changeset-based approach to assess source code density and developer efficacy</em>&quot; and has since been extended to support extended analyses.},