bugfix in getpixscale.
when CDELT1/2 are filled, but both are 1, use the CD matrix.
added imports and __all__ to __init__.py
added computeScaling2to1.
  (a function for scaling the combination of two band passes to match a third.
   e.g.   matching J+H to F140W. )
trivial bug fixes. Removed getpixscale()