Update to readthedocs config v2

.readthedocs.yml

@@ -1,14 +1,16 @@
-# http://docs.readthedocs.io/en/latest/yaml-config.html#requirements-file
+# https://docs.readthedocs.io/en/latest/config-file/
+version: 2
 
-# Don't build any extra formats
 formats:
-  - none
+  - htmlzip
 
 build:
   image: latest
 
 python:
-  version: 3.6
-  pip_install: true
-  extra_requirements:
-    - docs
+  version: 3.7
+  install:
+    - method: pip
+      path: .
+      extra_requirements:
+        - docs