feat(splitter): chunking projectid, vaultid, start_marker and end_marker

This patch allows every vaultid specific to a projectid to be chunked
with a start marker and end marker. This allows the manager to be
instantiated with a different start and end marker when calling the
validation functions.

Addresses Issue: https://github.com/rackerlabs/deuce-valere/issues/10
Shouldn't chunks be either len(1), or len(0) or None? Thus the loop here is not required.

If there are no blocks, then you might want to rechunk based on the storage block list (changing the values from storage ids to metadata ids) in case it is sufficiently large.