added block_edges, added statsutils
added rebin to specutils

wraps the my_numpy rebin function to automate dealing with fluxes and
errors
first draft coadd func in specutils
overhauled mids2edges
reversed order of polyfit_binned coeffs

now they match polyfit, so they can be used with polyval. also looks
like I changed some stuff with mids2edges -- don't know what that's
about
relaxed the criterion even-sized bins in pcolor_reg
revamped rebin to be faster
revamped common grid to be faster

not as good -- it can oversample -- but way faster than the old version
added quadsum

and some other changes