message: [new feature] Card: add lazy-load prop
diff: >
  <slot name="thumb">
  <img
  + v-if="lazyLoad"
  + v-lazy="thumb"
  + :class="b('img')"
  + >
  + <img
  + v-else
  :src="thumb"
  :class="b('img')"
  >
  @@ -81,6 +87,7 @@ export default create({
  thumb: String,
  title: String,
  centered: Boolean,
  + lazyLoad: Boolean,
  thumbLink: String,
  num: [Number, String],
  price: [Number, String],
  