Import submodules for bloat and webtreemap.

This project is a lazy person's way to visualise bloat and saves you
having to check out two projects and write a bash script to easily
visualise results.

It uses the "bloat" and "webtreemap" projects from Evan Martin and
next to nothing else.

[1] https://github.com/martine
Add bloat.sh helper script, some example images and a howto in the README.