Reduce inference (round 2)

Continuing [#228](https://github.com/scalanlp/breeze/pull/228) 

I think I may have shaved 10 sec off a full rebuild on my system, but I can't be sure d/t trial-to-trial variability... for my information, what is the best way to profile a compile?

At least IntelliJ is much more responsive when editing scala.linalg.package, DM, and DV...