Added gprof parsing fucntionality. Gprof call graph output can now be parsed and turned into a networkx directed call graph data structure. Separated Call class into cflow and gprof variants that contain their respective tool's parsing implementation details. Moved Stack from the attacksurfacemeter module into the loades module. Lots of tests broken. As of now, many of the calculated metrics don't work with gprof parsed call graphs due to gprof's lack of information regarding C library calls.
Fixed import in Stack test suite.
Fixed unit tests
Added gprof sample output files for ffmpeg and helloworld.