start of mods for triangles
working on counting triangles
Merge branch 'master' into clustering
fixing count-tri
cleaning up triangle counter
Merge branch 'master' into clustering

Conflicts:
	util/Makefile
- First working version of triangle counting
Node: added get_nbrs_ref to pass a const reference back to the neighbor list
Graph: changed is_edge() to get_nbrs_ref instead of passing copies of the neighbor list
Smarter edge_listing traverses edge lists instead of every possible pair of edges
code prettification
fix leaked file

added method to Graph to return a const reference to the degree vector

Added AdjacencyList writer to GraphWriter

implement clustering coefficient calculations

example driver/main counting triangles and computing clutering coefficients

Added new edgelist to adjacencylist converter
Futz around with makefiles to enable parallel gnu make to work
removing extra debugging junk
Fix tests to use new graph i/o code; add test for next labels
Fix off-by-one bug in Graph creation when specifying initial node count to constructor