Used "readelf -d | grep NEEDED" on the compiled modules to make sure we only
require what is actually needed at runtime.
Double checked documented runtime dependencies on Python modules, grepped the sources
for the "dependencies" I removed, and smoke tested the provided "cmd:"s after install.
Cleaned up build requirementes while at it. In particular, cmd:pip wasn't actually
required, (and we should avoid using it on recipes, in any case, IMO, at least in a way
we don't control, and using "--no-deps" while at it).
