make entry page to ProMod3 a bit more informative

Reason for that is that we don't want to create a fancy website
but rather host the static doc somewhere.

doc/index.rst

-.. ProMod3 documentation master file, created by
-   sphinx-quickstart on Thu Oct 10 23:17:00 2013.
-   You can adapt this file completely to your liking, but it should at least
-   contain the root `toctree` directive.
+ProMod3
+=======
 
-Welcome To ProMod3's Documentation!
-===================================
+ProMod3 is a modelling engine based on the OpenStructure [biasini2013]_ 
+computational structural biology framework that can perform all steps required 
+to generate a protein model by homology. Its modular design aims at 
+implementing flexible modelling pipelines and fast prototyping of novel 
+algorithms.
 
-Contents:
+
+Documentation
+=============
 
 .. toctree::
    :maxdepth: 2
@@ -18,11 +21,7 @@ Contents:
    :maxdepth: 1
 
    changelog
-   
 
-Indices And Tables
-==================
 
-* :ref:`genindex`
-* :ref:`modindex`
-* :ref:`search`
+.. [biasini2013] Biasini M, Schmidt T, Bienert S, Mariani V, Studer G, Haas J, Johner N, Schenk AD, Philippsen A and Schwede T (2013). OpenStructure: an integrated software framework for computational structural biology. Acta Cryst.
+