Added delta hyperbolicity code along with corresponding gtests.
The gtests cover connected and disconnected graphs.
Currently, requires omp to compile and run.
Merge remote branch 'upstream/master'
Merge branch 'master' into features

Conflicts:
	lib_graphd/inc/GraphProperties.h
	lib_graphd/src/GraphProperties.cpp
Added powerlaw and delta hyperbolicity to graph_stats.cpp
Merge remote branch 'upstream/master' into merge_test

Conflicts:
	util/src/graph_stats.cpp
Merging powerlaw and delta hyperbolicity code from Schrock