fix: implement fix from @benfoxall for 'chained tweens get out of syn…

…c with sporadic updates'. Closes #187

src/Tween.js

@@ -361,7 +361,9 @@ TWEEN.Tween = function (object) {
 				}
 
 				for (var i = 0, numChainedTweens = _chainedTweens.length; i < numChainedTweens; i++) {
-					_chainedTweens[i].start(time);
+					// Make the chained tweens start exactly at the time they should,
+					// even if the `update()` method was called way past the duration of the tween
+					_chainedTweens[i].start(_startTime + _duration);
 				}
 
 				return false;

test/unit/tests.js

@@ -839,7 +839,29 @@
 				test.equal( TWEEN.getAll().length, 0 );
 				test.done();
 
-			}
+			},
+
+			'Test TWEEN.Tween.chain progressess into chained tweens': function(test) {
+
+				var obj = { t: 1000 };
+
+				// 1000 of nothing
+				var blank = new TWEEN.Tween({}).to({}, 1000);
+
+				// tween obj.t from 1000 -> 2000 (in time with update time)
+				var next  = new TWEEN.Tween(obj).to({ t: 2000 }, 1000);
+
+				blank.chain(next).start(0);
+
+				TWEEN.update(1500);
+				test.equal(obj.t, 1500);
+
+				TWEEN.update(2000);
+				test.equal(obj.t, 2000);
+
+				test.done();
+
+			},
 
 		};