Small util fixes and updated example sources

This depends on #17, so the PR is against the `config` branch. Change to be against master, once #17 is merged.

- small tweaks to code maintenace utils
- sources point to custom branch of rosdistro containing converted rules files
- use the provided testing sources and cache by running from the directory of
  the xylem source checkout:

      xylem resolve boost --prefix prefix