Bug 1384167 - Add a config file for pyup. (#658)

We want to have the pyup service regularly check our requirements files for security update. Adding this config file is the first step to setup this process.

.pyup.yml

@@ -0,0 +1,10 @@
+schedule: "every day"
+search: False
+update: insecure
+requirements:
+  - requirements.txt:
+      update: security
+  - requirements-dev.txt:
+      update: security
+  - docs/requirements.txt:
+      update: security