fix 调用play和pause后样式没有自动变更的问题

demo/main.js

@@ -13,3 +13,5 @@ mePlayer({
 document.querySelector('button').addEventListener('click', function () {
     mePlayer.toggleTheme();
 });
+
+mePlayer.play();

dist/meplayer.js

@@ -244,12 +244,14 @@
 
 	    function play() {
 	        if (audio.paused) {
+	            utils.addClass(meplayerContainer, 'meplayer-isplaying');
 	            audio.play();
 	        }
 	    }
 
 	    function pause() {
 	        if (!audio.paused) {
+	            utils.removeClass(meplayerContainer, 'meplayer-isplaying');
 	            audio.pause();
 	        }
 	    }

src/js/main.js

@@ -193,12 +193,14 @@ root.mePlayer = function (options) {
 
     function play() {
         if (audio.paused) {
+	        utils.addClass(meplayerContainer, 'meplayer-isplaying');
             audio.play();
         }
     }
 
     function pause() {
         if (!audio.paused) {
+	        utils.removeClass(meplayerContainer, 'meplayer-isplaying');
             audio.pause();
         }
     }