Fix bug when opts.columns specified

```
Uncaught TypeError: Cannot read property 'find' of undefined cdn.livefyre.com/libs/streamhub-wall/v3.0.6/streamhub-wall.min.js:8085
```
```this.setColumns``` expects ```this.$el``` to be defined. But the parent ```ContentListView``` constructor has not been invoked and therefore ```this.$el``` is undefined.