Correlate: Rework lag/bin calculation
Correlate: Finally get lag calculation right

I don't think the previous approach was wrong per se but it did produce
counter-intuitive jumping about
Correlate: Kill debug output
Tighten up Correlate abstractions
Move correlate to new package
SparseCorr: Rewrite rebin with stream fusion

This makes things about 10% faster, although this may be due to change
to integer math
Correlate: Compute dot and dot-squared in one pass

This gives roughly a factor of 2 speed-up
Bump pipes-bytestring and pipes-vector