Made the internal dict a default dict.
Added order. Stores index, data by order added.

The idea is that by storing this order, you can just add everything in
your simulation to the bootstrapper and have a fairly complete story of
what went on.

Later, might want to have something that does some introspection and
figures out which class or function added that item. Just a nice extra
peice of info.
Added git.py.

So far, contains commands to get the current revision number, or the SHA
of the current commit.
Added flush argument to bootstrapper.print_summary

Can flush the file before closing it.