intro doc added

doc/index.rst

-.. ESS Python Tools documentation master file, created by
-   sphinx-quickstart on Mon Oct 24 13:30:56 2016.
-   You can adapt this file completely to your liking, but it should at least
-   contain the root `toctree` directive.
-
 Welcome to ESS Python Tools's documentation!
 ============================================
 
+This is the automatic documentation of the ESS Python tools developed by the beam physics group.
+
+The sources can be found on GitLab_.
+
+Installation is easiest using pip. If you want to install just for your user type
+
+.. code-block:: bash
+    pip install git+https://gitlab01.esss.lu.se/ess-bp/ess-python-tools.git -U --user
+
+If you want to install it system wide, omit the `--user` argument:
+
+.. code-block:: bash
+    pip install git+https://gitlab01.esss.lu.se/ess-bp/ess-python-tools.git -U
+
+
+.. _GitLab: https://gitlab.esss.lu.se/ess-bp/ess-python-tools/
+
+
 Contents:
 
 .. toctree::