Cleaned up examples Makefile
ChainBinomial_Sim bugfix

If the transmissibility or infectious period were changed after constructing
the simulation, the transmission-day probability distribution was not being
updated.
Improved min path length calculations

Some optimizations to path length calculations; added a get_node_by_name()
function.
K-shell decomposition added

Seems to be working, and pretty fast.
Merge branch 'master' of github.com:tjhladish/EpiFire

Conflicts:
	src/ChainBinomial_Sim.h