Implemented parsing of input files (located in reader.h and reader.cc).  You can now feed arbitrary topologies and failure events (ie. link/switch up/down) into
the simulation.  I've further implemented heartbeats being broadcasted based on a timer.  These changes are sufficient for the complete simulation of broadcasts
(without controllers).  I've verified by hand these changes on the topology square_broadcast.yaml with events contained in square_bcast_events.yaml.

The code could now use some cleaning up- including making it again independent of broadcasting and editing it to be in a form that satisfies the Google style
guide.  I will add a Makefile and a description of the input file format sometime soon.