Add lockfile; remove dead list.
Add garbage collection to EFT.
Basic snapshots.
Hashes are now always [32]byte, because that's actually what they are.
Add Checkpoint()
Yay! A tree bug!
Block hashes and file hashes are different. Good times.
Add a HmacSlice function.
Some more work on upload logic.
Merge pull request #1 from NatTuck/eft-gc

Eft gc