fixed up the dispersion attribute handlers
update to @keflavich's equivalencies - furthermore update to `Legendre1D`.
adding wcs information grabber
added `FITSWCSSpectrum` fits keyword parser.
two readers are implemented using the information class.
deleted fits reader in wcs.
this was the last link to fits in specwcs for now.
added ordered dictionary for the WAT keywords according to @mhvk's suggestion.
Merge pull request #41 from wkerzendorf/fits_wcs_cleanup

FITS WCS cleanup