add readthedocs config

.readthedocs.yml

@@ -0,0 +1,22 @@
+# Required
+version: 2
+
+# Build documentation in the docs/ directory with Sphinx
+sphinx:
+  configuration: docs/conf.py
+
+# Build documentation with MkDocs
+#mkdocs:
+#  configuration: mkdocs.yml
+
+# Optionally build your docs in additional formats such as PDF and ePub
+formats: all
+
+# Optionally set the version of Python and requirements required to build your docs
+python:
+  version: 2.7
+  install:
+    - method: setuptools
+      path: .
+    - requirements: dev-requirements.txt
+    - requirements: requirements.txt