[paper] use new porepy reference

paper.bib

@@ -110,13 +110,14 @@ keywords = "Fracture networks, DFN, Stochastic modeling, Open source, Matlab, Fl
   Doi       = {10.1007/s13137-019-0116-8},
 }
 
-@TechReport{keilegavlen2017,
-  author      = {Keilegavlen, Eirik and Fumagalli, Alessio and Berge, Runar and Stefansson, Ivar and Berre, Inga},
-  title       = {PorePy: An Open Source Simulation Tool for Flow and Transport in Deformable Fractured Rocks},
-  institution = {arXiv:1712.00460 [cs.CE]},
-  year        = {2017},
-  owner       = {elle},
-  timestamp   = {2017.07.08},
+@article{keilegavlen2020porepy,
+  title={PorePy: an open-source software for simulation of multiphysics processes in fractured porous media},
+  author={Keilegavlen, Eirik and Berge, Runar and Fumagalli, Alessio and Starnoni, Michele and Stefansson, Ivar and Varela, Jhabriel and Berre, Inga},
+  journal={Computational Geosciences},
+  pages={1--23},
+  year={2020},
+  publisher={Springer},
+  doi={10.1007/s10596-020-10002-5}
 }
 
 @Article{gmsh2009,

paper.md

@@ -34,7 +34,7 @@ a variety of CAD file formats for subsequent post-processing or meshing
 with other software. Besides that, output routines to the geometry file format
 of Gmsh ([gmsh.info/](https://www.gmsh.info/); @gmsh2009) are provided,
 which is an open-source mesh generator that is widely used in academic research
-on numerical methods (see e.g. @keilegavlen2017; @berge2019).
+on numerical methods (see e.g. @keilegavlen2020porepy; @berge2019).
 The code is written in C++, but Python
 bindings are provided that allow users to access all functionality from Python.