Added setFilter(), containerID and getFilter() to (#1360)

mock slice object in exploreV2

 - filter_box in exploreV2 was broken because containerID and
   getFilter() were not defined in the mock of slice object

caravel/assets/javascripts/explorev2/components/ChartContainer.jsx

@@ -32,6 +32,8 @@ class ChartContainer extends React.Component {
 
   getMockedSliceObject() {
     return {
+      containerId: this.props.containerId,
+
       jsonEndpoint: () => this.props.jsonEndpoint,
 
       container: {
@@ -62,6 +64,16 @@ class ChartContainer extends React.Component {
 
       selector: this.state.selector,
 
+      setFilter: () => {
+        // set filter according to data in store
+        // used in FilterBox.onChange()
+      },
+
+      getFilters: () => (
+        // return filter objects from viz.formData
+        {}
+      ),
+
       done: () => {
         // finished rendering callback
       },