Ensure starting from any transparent value uses the endpoint as its c…

…olor the whole way through - Fixes #32

jquery.color.js

@@ -315,7 +315,8 @@ color.fn = jQuery.extend( color.prototype, {
 		var end = color( other ),
 			spaceName = end._space(),
 			space = spaces[ spaceName ],
-			start = this[ space.cache ] || space.to( this._rgba ),
+			startColor = this.alpha() === 0 ? color( "transparent" ) : this,
+			start = startColor[ space.cache ] || space.to( startColor._rgba ),
 			result = start.slice();
 
 		end = end[ space.cache ];

test/unit/color.js

@@ -267,7 +267,7 @@ test( ".transition() works with $.Colors", function() {
 		trans = jQuery.Color( "transparent" ),
 		fifty = black.transition( whiteAlpha, 0.5 );
 
-	expect( 12 );
+	expect( 16 );
 	testParts( fifty, {
 		prefix: "black -> whiteAlpha 0.5",
 		red: 127,
@@ -289,6 +289,15 @@ test( ".transition() works with $.Colors", function() {
 		blue: 255,
 		alpha: 0.25
 	});
+
+	// fixes issue #32
+	testParts( jQuery.Color( 255, 0, 0, 0 ).transition( black, 0.5 ), {
+		prefix: "transparent red -> black 0.5",
+		red: 0,
+		green: 0,
+		blue: 0,
+		alpha: 0.5
+	});
 });
 
 test( ".transtion() works with strings and objects", function() {