v0.1.0, 7/28/15 -- Initial release.
v0.1.1, 7/28/15 -- Slight changes in names.
v0.1.3, 7/30/15 -- Moved node_value function into problem and changed priorityqueue to priority set implemented using blist
v0.1.4, 7/30/15 -- Removed print statements
v0.1.5, 7/30/15 -- Fixed bug in updating path
v0.1.6, 7/31/15 -- Removed uuid because it is slow
