Change dx, xw parameters into scale to match usage in image.scale, which is what the all really mean.
(#364)
Change C++ Image class name to ImageAlloc
(#364)
Refactor Image class to have single python-layer class that contains an item that is some kind of C++ layer Image object
(#364)
Strip image.scale out of C++ layer so it is only in python layer
(#364)
Convert the use of scale as a float to an implicit PixelScale WCS object.
(#364)
Add new features so far to CHANGELOG
(#364)
Minor doc and comment edits that I noticed while writing the CHANGELOG
(#364)
More edits to CHANGELOG
(#364)
Some changes to WCS API based on comments.  SKy -> World, Chip -> Image, apply methods -> overloaded toImage,toWorld functions
(#364)
Merge branch 'master' into #364a

Conflicts:
	CHANGELOG.md
	galsim/optics.py
Some updates to WCS class structure
(#364a)
typo
(#364a)
Fix writing header with scale == None
Let python handle position +=, *=, etc so python ops act more like python ops normally do.
(#364a)
Fix error in lensing interpolation that got missed because tests used to use grid_spacing=1.
(#364a)
typos, punctuation, line width, etc.
Various typos and wording edits based on Rachels comments
(#364a)
Update C++ SBBox to use width, height to match python Box class
(#364a)
Remove python wrapping of PhotonArray, since we don't need that.
(#364a)
Remove previously deprecated Ellipse class
(#364a)