Reverting Vector3.angleTo change. See #7343.

src/math/Vector3.js

@@ -655,7 +655,7 @@ THREE.Vector3.prototype = {
 
 	angleTo: function ( v ) {
 
-		var theta = this.dot( v ) / Math.sqrt( this.lengthSq() * v.lengthSq() );
+		var theta = this.dot( v ) / ( this.length() * v.length() );
 
 		// clamp, to handle numerical problems