Add py36 to tox and a note to myself to remember to activate pyenv be…

…fore using tox

tox.ini

@@ -1,5 +1,5 @@
 [tox]
-envlist = py26,py27,py33,py34,py35
+envlist = py26,py27,py33,py34,py35,py36
 
 [testenv]
 downloadcache = .tox/_download/
@@ -21,3 +21,12 @@ commands = py.test -v --junitxml={envlogdir}/result.xml coursera/test
 # {opts} is remove to prevent passing option "--download-cache" to pip
 # which is already gone.
 install_command = pip install {packages}
+
+# Notes for developers. Depending on your system configuration,
+# you may find this bash function useful to run before running tox:
+#
+# activate_pyenv () {
+#         export PYENV_ROOT="$HOME/.pyenv"
+#         export PATH="$PYENV_ROOT/bin:$PATH"
+#         eval "$(pyenv init -)"
+# }