Fixed eslint problems

lib/pixi/button.js

@@ -1,3 +1,4 @@
+/* global PIXI TweenLite */
 import Theme from './theme.js'
 import Tooltip from './tooltip.js'
 import Badge from './badge.js'
@@ -244,6 +245,7 @@ export default class Button extends PIXI.Container {
             TweenLite.to([this.button, this.content], this.theme.fast, { alpha: 1, overwrite: 'none' })
         })
 
+        // eslint-disable-next-line no-unused-vars
         this.button.on('pointerdown', e => {
             //this.capture(e)
             TweenLite.to([this.button, this.content], this.theme.fast, { alpha: .7, overwrite: 'none' })