Keep file format documentation in the repo

The format documentation should be packaged with and versioned with the
library.

cbugg: closes bug-204

http://cbugg.hq.couchbase.com/bug/bug-204

Change-Id: If9be65f6902e16f85aa4649f2ed38d94daf42714
Reviewed-on: http://review.couchbase.org/24435
Reviewed-by: Fulu Li <fulu@couchbase.com>
Tested-by: Aaron Miller <apage43@ninjawhale.com>