Revised random number generator initialization for speedup.
Added R-MAT and RIG generators to GraphCreator.
Fixing code to work with disconnected graphs/take largest components

    let avg_path_length handle disconnected graphs
    Fix avg_path_length so it compiles
    Changes to accomodate getting a largest component from a graph without first writing it to do, or requiring weights
    Don't try to record number of hops for vertices an infinite distance away
    correct some output functions
    Ensure that boost algorithm uses our distance for infinity
    Add option to graph_stats to record timing to file in addition to stdout
    cleaning up code
Change deg. dist output to: 'degree value' instead of just 'value'
Add APSP matrix output functions
add new method to specify writing of apsp matrix
Fix merge conflicts with spacing in student code and Matt's file append code