清除多余样式，实现高度宽度自适应，放置App.vue中

#app {
  font-family: 'Avenir', Helvetica, Arial, sans-serif;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  width:100%;
  height:100%;
}
*{
  margin:0;
  padding:0;
  box-sizing:border-box;
}
html,body{
  width:100%;
  overflow-x:auto!important;
}
ul{list-style:none}
li {list-style:none;}
a{text-decoration: none;} 
img{vertical-align:top;border:none}
table {border-collapse:collapse;border-spacing:0;}
input,textarea,select {font-family:inherit;font-size:100%;font-weight:inherit;}

.clearf:after,
.clearf:before{
    content:"";
    display:block;
    clear:both;
}