restore spinner slot, add test

Author: bartekupartek

src/components/InfiniteLoading.vue

@@ -1,7 +1,9 @@
 <template>
   <div class="infinite-loading-container">
     <div v-show="isLoading">
-      <spinner :spinner="spinner" />
+      <slot name="spinner">
+        <spinner :spinner="spinner" />
+      </slot>
     </div>
     <div class="infinite-status-prompt" v-show="isNoResults">
       <slot name="no-results">No results :(</slot>

test/unit/specs/InfiniteLoading.spec.js

@@ -345,6 +345,24 @@ describe('vue-infinite-loading', () => {
     vm.$mount('#app');
   });
 
+  it('should interpolate custom spinner slot', (done) => {
+    vm = new Vue(Object.assign({}, basicConfig, {
+      mounted: function mounted() {
+        expect(this.$el.querySelector('.icon-spinner')).to.be.not.null;
+        done();
+      },
+      template: `
+        <infinite-loading>
+          <div slot="spinner">
+            <i class="icon-spinner"></i>
+          </div>
+        </infinite-loading>
+      `,
+    }));
+
+    vm.$mount('#app');
+  });
+
   it('should support hide load result through blank slots', (done) => {
     let calledTimes = 0;