Backend support for organization IP ranges.

We can now store IP ranges with Organizations. The aim is to have any user
logging in with a remote IP address within such a race will get the
organization roles assigned to the user object stored in the Flask session.

This commit just contains the MongoDB storage and querying, and not yet the
updates to the user.

requirements.txt

@@ -20,6 +20,7 @@ Flask-WTF==0.12
 gcloud==0.12.0
 google-apitools==0.4.11
 httplib2==0.9.2
+IPy==0.83
 MarkupSafe==0.23
 ndg-httpsclient==0.4.0
 Pillow==4.1.1