[BACK_INCOMPAT] Initialization of `fabric.Image.filters.Tint` is now different - options.color: color string value, options.opacity: 0..1
Now you can define opacity of the tint filter (by rgba/hsla colors or with opacity attribute)
Doc additions
Fixed unit test
Merge pull request #862 from Kienz/tintFilter

[BACK_INCOMPAT] Initialization of `fabric.Image.filters.Tint` is now different