Get a more midsized graph for testing

[danieldzahka]

The 11GB twitter graph takes too long for quick testing, that also stresses TBB a bit. Download a graph from here, that is more in the 1MB size range (in CSR form that is).

1. Pick a graph
2. Encode it into .idx/.adj format using tool.
3. Generate the reference outputs using galois, and add them to the algorithm_tests.cpp file
4. Add the new file to the existing small test cases. Add to the GENERATE() in catch