Merge pull request #26 from laurentheirendt/update-citation

update of citation

Author: laurentheirendt

README.rst

@@ -207,8 +207,8 @@ paper of The COBRA Toolbox shall we cited when referring to the ``MATLAB.devTool
     A. Saunders, Costas D. Maranas, Nathan E. Lewis, Thomas Sauter,
     Bernhard Ø. Palsson, Ines Thiele, Ronan M.T. Fleming, **Creation and
     analysis of biochemical constraint-based models: the COBRA Toolbox
-    v3.0** (submitted), 2017,
-    `arXiv:1710.04038 <https://arxiv.org/abs/1710.04038>`__.
+    v3.0**, Nature Protocols, volume 14, pages 639–702, 2019
+    `doi.org/10.1038/s41596-018-0098-2 <https://doi.org/10.1038/s41596-018-0098-2>`__.
 
 .. end-how-to-cite-marker