Add Petsc and Slepc options to build system
Initial version of eigen spectrum solver
Bug fixes.
spelling errors
sorted out merge of graph_stats.cpp
Power law fitting added to GraphProperties
create a self tester for eigen solver, requres a define at compile time
Merge branches 'josh-upstream' and 'eigen_spectrum'
Power Law fitting added to GraphProperties and compiles. Added a gtest, but currently doesn't work.
Merge pull request #28 from MattBBaker/master

Adding eigenspectrum from Matt
Power law fitting has been added as well as a gtest for it.
Need boost/math/special_functions/zeta.hpp and accompanying headers to compile.
Also, the directory holding these headers needs to be included in lib_graphd/src/Makefile
Merge branch 'features'