Summary:
I trimmed the previous versions of this down a lot to only
focus on what RN developers need to know without duplicating
what we have in the non-RN docs.
Reviewed By: mweststrate
Differential Revision: D20816115
fbshipit-source-id: 9d88a6fb0d49e823194cce647e64b86d61d6229a
2823307c62