Suggestion collections: Tiers and Sharding

[jbenet]

Suggest collections:

• tiered-blob-store -- layered access (for caches, local vs remote, etc) -- https://github.com/datastore/datastore#hello-tiered-access
• sharded-blob-store -- shard on the key across multiple - https://github.com/datastore/datastore#hello-sharding

[jnordberg]

Could those not be implemented as a module that takes abstract-blob-store compatible stores?