fix compatibility docs

Author: IgnacioHeredia

doc/source/index.rst

@@ -19,16 +19,18 @@ fron of their model, thus accesing its functionality via HTTP calls.
 Compatibility
 -------------
 
-The DEEPaaS API works with Python 2.7+ and Python 3.
+The DEEPaaS API works with Python 3.5.3 or higher.
 
 Upgrading from V1 of the API
 ############################
 
-The DEEPaaS API provides two different API versions: V1 and V2. V1 was the
-initial API version, supported in releases under ``1.0.0``.  Starting with the
-``1.0.0`` release V2 is the only version supported, with the V1 of the API
-disabled by default. Please, read carefully the :ref:`upgrade-notes` before
-upgrading to a newer version.
+The DEEPaaS API provides two different API versions: V1 and V2.
+V1 was the initial API version, supported in releases under ``1.0.0`` and
+compatible with Python 2.7+ and Python 3.
+Starting with the ``1.0.0`` release V2 is the only version supported and
+requires Python 3.5.3 or higher.
+Please, read carefully the :ref:`upgrade-notes` before upgrading to a newer
+version.
 
 Installation and upgrade documentation
 --------------------------------------