Show a diagram of timeflow in the callgraph.
Thickness of lines repesents amount of time spend in that subgraph
Redness of squares represents mount of time spent by self, not by descendants

usage:

$ profily --dot callgraph.dot myscript.py
$ dot -T pdf callgraph.dot > callgraph.pdf
$ open callgraph.pdf

TODO:
- figure out how to profile a generator that was created elsewhere
- add more control over the output to the commandline