make kwant paper reference point to NJP

content/citing.txt

@@ -12,7 +12,7 @@ to the description of your numerical calculations.  In addition, we ask you to
 cite the main paper that introduces Kwant:
 
   C. W. Groth, M. Wimmer, A. R. Akhmerov, X. Waintal, *Kwant: a software package
-  for quantum transport*, `arXiv:1309.2926 <http://arxiv.org/abs/1309.2926>`_.
+  for quantum transport*, `New J. Phys. **16** 063065 <http://iopscience.iop.org/1367-2630/16/6/063065>`_.
 
 
 Other references we ask you to consider