docs: create a support channel document

Author: Midnighter

.github/SUPPORT.rst

@@ -0,0 +1,17 @@
+=======
+Support
+=======
+
+* The mailing list is a good place to ask about general modeling questions.
+  Please use Google's excellent search capabilities before posting a new
+  question. By writing a well formulated question, with sufficient detail, you
+  are much more likely to quickly receive a good answer! Please refer to these
+  `StackOverflow guidelines <https://stackoverflow.com/help/how-to-ask>`_ on how
+  to ask questions.  `Google Group <http://groups.google.com/group/cobra-pie>`_
+* There is the cobrapy `gitter chat <https://gitter.im/opencobra/cobrapy>`_ where
+  you can ask questions as well. It is a bit more developer-centric than the
+  mailing list.
+* You can post questions in `GitHub issues
+  <https://github.com/opencobra/cobrapy/issues>`_, too. Please reserve this
+  channel for code problems and reserve conceptual questions for the mailing
+  list.