made setup.ml invocation more robust.

also updated dependency list, and made a note about an actual source of
up-to-date dependencies.
The previous solution was to clever...

Indeed this def_piqic is a crude hack, that I would like to remove,
since we really do not need this piqi.
Merge pull request #6 from ivg/piqi-setup-robustness

made setup.ml invocation more robust.
make README documentation clearer