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
That was my first thought as well. But I ran into some issues there.

I need to know the length of list of all meta_markers to make sure that the number of iterations are correct. 
One other problem could be that if there are enough orphaned blocks, the start marker and end marker, could end up being the same. That is why I need to separate out all the unique meta_markers ( metadata part of storage_ids) first and then apply the limits.