Clean up.

src/math/Quaternion.js

-import { _Math } from './Math.js';
-import { Vector3 } from './Vector3.js';
-
 /**
  * @author mikael emtinger / http://gomo.se/
  * @author alteredq / http://alteredqualia.com/
@@ -8,6 +5,9 @@ import { Vector3 } from './Vector3.js';
  * @author bhouston / http://clara.io
  */
 
+import { _Math } from './Math.js';
+import { Vector3 } from './Vector3.js';
+
 function Quaternion( x, y, z, w ) {
 
 	this._x = x || 0;
@@ -18,8 +18,9 @@ function Quaternion( x, y, z, w ) {
 }
 
 Object.assign( Quaternion, {
+
 	isQuaternion: true,
-	
+
 	slerp: function ( qa, qb, qm, t ) {
 
 		return qm.copy( qa ).slerp( qb, t );