Updating READMI with reStructuredText equivalent of Gitter chat badge. Ref #13

Author: myroslav

README.md

@@ -7,6 +7,10 @@
 .. image:: https://readthedocs.org/projects/openprocurementapi/badge/?version=latest
     :target: http://api-docs.openprocurement.org/
 
+.. image:: https://badges.gitter.im/Join%20Chat.svg
+    :target: https://gitter.im/openprocurement/openprocurement.api?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge
+    :alt: Gitter
+
 Documentation
 =============