Add Wagtail Flags from CFPB (#25)

https://github.com/cfpb/wagtail-flags

README.md

@@ -73,6 +73,7 @@ Awesome Wagtail [![Awesome](https://cdn.rawgit.com/sindresorhus/awesome/d7305f38
 ### Settings management
 
 - [Wagtail-Constance](https://github.com/MechanisM/wagtail-constance) - django-constance integration for Wagtail CMS.
+- [Wagtail-Flags](https://github.com/cfpb/wagtail-flags) - Feature flags for Wagtail sites.
 
 ### E-commerce