Add L_PREFER_CANVAS for huge speedup over SVG
Complain about undefined callbacks but don't try to invoke them
Merge pull request #41 from enthought/enh/prefer-canvas

Add L_PREFER_CANVAS for huge speedup over SVG
Merge branch 'master' into enh/visualize-salt-field
Merge pull request #43 from enthought/fix/undefined-callbacks

Harden against mistakes when using HOFs
Merge branch 'master' into enh/visualize-salt-field

Conflicts:
	static/js/API.js
	static/js/Models.js
Contour config overrides data values
Redrawing without a callback is perfectly normal, thank you.
0.3 is too low. Let's try 0.5.