README updated for new CLI
giraph-debug command-line options for DebugConfig

`-S SUPERSTEP_NO` and `-V VERTEX_ID` and `-N` for debugNeighbors.
giraph-debug option (-C) for explicitly passing Computation classes to instrument
README update with new command-line options
Merge pull request #41 from netj/cli-options

CLI options for giraph-debug script