Summary:
This could help people understand what's different essentially, and make better
decision on what to use.
Test Plan: Seems the vim spell checker is happy.
Reviewers: #sourcecontrol, rmcelroy, stash
Reviewed By: rmcelroy, stash
Subscribers: mjpieters
Differential Revision: https://phabricator.intern.facebook.com/D4203039
Signature: t1:4203039:1479461745:9cce0239088707bd8b66055ba66c420e97a3bd03