Fix duplication of entries in infinite scroll

Fixes #1242

- Switched to render each new item as its added to the collection when
retrieving via scroll checks.
- Added check to remove all subviews whenever `render` is called on
`ContentList` as a preventative measure.
- Cached the jquery reference to the ordered list in `render`.
Merge pull request #1258 from gotdibbs/Issue1242

Fix duplication of entries in infinite scroll