updated test to use json_encode
Revert "Cherry-picked 86038fa6e5347f1e87fcd9fb3c6539bb5201c462 and fixed conflicts, so FileDataStore uses YAML instead of marshal"

This reverts commit 2b4efc28d450cafb20234941c8a1f799023f508e.
Revert "Cherry-picked 78d7ae64ac966794753e1d6b13f5ecfc7eb274a7 : S3 meta now uses simple x-amz-meta headers (but still works with x-amz-meta-extra header)"

This reverts commit f70da3cb923b36710091ecf3422253ca2732c06f.
Revert "Cherry-picked 8805394fcfd0de9be88f7d680bd0d48d29ff72b7: Mongo meta uses actual meta hash, not marshal dump"

This reverts commit 7bcf62bccf1685661d210217170258fece48c3f5.

Conflicts:
	lib/dragonfly/data_storage/mongo_data_store.rb
Revert "Cherry-picked 88eaa4bab0473fa8fb70fd5a0957ff3278b7f5d4 : Couch meta is just stored in the normal way as an object, although the old marshal dumped version will still work"

This reverts commit 92ae6197d850a8e13569ff57f363b63b6fa79c07.