docs: Bump version number in documentation.

docs/conf.py

@@ -52,10 +52,10 @@ copyright = u'2014-2019, ESnet'
 # built documents.
 #
 # The short X.Y version.
-version = '3.6'
+version = '3.7'
 # The full version, including alpha/beta/rc tags.
 
-release = '3.6'
+release = '3.7'
 
 # The language for content autogenerated by Sphinx. Refer to documentation
 # for a list of supported languages.