A simple script to generate a graph cloud from a set of ruby stack
traces. Stack traces must be separated by a line consisting of '--',
the output of 'grep -A' on a log file containing these stack traces.

Depends on the ruby-graphviz gem, and, by extension, graphviz.

Usage: ruby-call-graph.rb -i INPUT -o OUTPUT [-t THRESHOLD]
    -i, --input INPUT                Input stack trace (- for stdin)
    -o, --output OUTPUT              Output filename
    -t, --threshold THRESHOLD        Edge/Node Count Threshold. Defaults to 100
    -h, --help                       Show this message