Merge pull request python#40 from ned-deily/patch-2

Update for 3.7 branch creation and start of 3.8

Author: ewdurbin

build_docs.py

@@ -41,7 +41,8 @@
 BRANCHES = [
     # version, git branch, isdev
     (3.6, '3.6', False),
-    (3.7, 'master', True),
+    (3.7, '3.7', True),
+    (3.8, 'master', True),
     (2.7, '2.7', False)
 ]