Updated the R graph clustering example to use the new derived_graph_t.
Also updated the fielder clustering to use principle components.
Updated the c-fielder-igraph app to use the new graph_t struct correctly.
Added some documentation and cleaned up the R hashbang script.
Updated README.md.
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Merge pull request #17 from aterrel/webgraph_app

Webgraph app
Updates to gunrock api
Pulling back in some code that was written over
debugging tangelo and webgraph