First crack at ds9 style color map shift/scale in X/Y

	modified:   ginga/FitsImage.py
	modified:   ginga/Mixins.py
	modified:   ginga/RGBMap.py
	modified:   ginga/gtkw/ColorBar.py
	modified:   ginga/imap.py
	modified:   ginga/qtw/ColorBar.py

- Ginga now uses a ds9 style color map change when using the interactive
    adjustment function
  - moving the cursor in Y adjusts the scale of the color map
  - moving the cursor in X adjusts the shift of the color map
Event handling updated

	modified:   ginga/FitsImageCanvas.py
	modified:   ginga/Mixins.py
	modified:   ginga/RGBMap.py
	modified:   ginga/gtkw/GingaGtk.py
	modified:   ginga/gtkw/PluginManagerGtk.py
	modified:   ginga/gtkw/plugins/Catalogs.py
	modified:   ginga/gtkw/plugins/Histogram.py
	modified:   ginga/gtkw/plugins/Pick.py
	modified:   ginga/gtkw/plugins/PixTable.py
	modified:   ginga/gtkw/plugins/Zoom.py
	modified:   ginga/misc/plugins/CutsBase.py
	modified:   ginga/qtw/GingaQt.py
	modified:   ginga/qtw/PluginManagerQt.py
	modified:   ginga/qtw/plugins/Catalogs.py
	modified:   ginga/qtw/plugins/Histogram.py
	modified:   ginga/qtw/plugins/Pan.py
	modified:   ginga/qtw/plugins/Pick.py
	modified:   ginga/qtw/plugins/PixTable.py
	modified:   ginga/qtw/plugins/Zoom.py

- Now provides default binding of color map warping with second mouse
    button
- Now provides default binding of porportional pan to first mouse button
- Both are disabled if a plugin has taken those bindings
Bump version info, updates to quick ref, manual

	modified:   ginga/doc/manual/manual.tex
	modified:   ginga/doc/manual/quickref.html
	modified:   ginga/version.py
Fix for setup.py to build on python3
Add .gitignore
Add .travis.yml