Hybrid Logical Clocks
An implementation of Hybrid Logical Clocks as described in "Logical Physical Clocks and Consistent Snapshots in Globally Distributed Databases", as found at http://www.cse.buffalo.edu/tech-reports/2014-04.pdf.
Forked from https://github.com/cstorey/hybrid-clocks, modified to more closely follow the paper, using timestamps that fit into 64-bits.