add citation

CITATION.rst

@@ -0,0 +1,21 @@
+Citing SimPEG
+=============
+
+There is a paper about SimPEG!
+
+
+    Cockett, R., Kang, S., Heagy, L. J., Pidlisecky, A., & Oldenburg, D. W. (2015). SimPEG: An open source framework for simulation and gradient based parameter estimation in geophysical applications. Computers & Geosciences.
+
+
+BibTex:
+-------
+
+```
+@article{cockett2015simpeg,
+  title={SimPEG: An open source framework for simulation and gradient based parameter estimation in geophysical applications},
+  author={Cockett, Rowan and Kang, Seogi and Heagy, Lindsey J and Pidlisecky, Adam and Oldenburg, Douglas W},
+  journal={Computers \& Geosciences},
+  year={2015},
+  publisher={Elsevier}
+}
+```

README.rst

@@ -35,6 +35,7 @@ The vision is to create a package for finite volume simulation with applications
 * supports 1D, 2D and 3D problems
 * designed for large-scale inversions
 
+.. include:: CITATION.rst
 
 Website:
 http://simpeg.xyz
@@ -57,4 +58,4 @@ https://github.com/simpeg/simpeg/issues
 
 
 Code Snippets & Tutorials:
-http://www.row1.ca/simpeg
+http://simpeg.xyz/Journal