added resample function to resample a spectrum on a different binning
Merge branch 'add_trapz' into dev with new function "resample"
(changed name from trapz)
Refactored and added access for wavelength dispersion resolution
Added some tests of util functions
refactor Legendre usage
Removed util.LegendreFit().  Yet another case of something obviously
useful already being in numpy.
Merge branch 'add_wdisp' into dev
make util.resample faster