added a simple specwcs framework
added a linear wcs and an init file. now testing
added a simple from_fits method for reading the keywords from a simple linear fits wcs
unified the lookup table wcs class
fixing up the spectrum1d class to be specwcs compliant
fixed up spectrum1d to work with initial specwcs
added dispersion and flux units
added uncertainty column to from_table
small fixes
fixed the flux_unit and dispersion_unit