synchronized row updates

[shaunc]

Issue to track #2 (comment).
We need a way to pull in content that is fast enough to stay in sync with fast scrolling.

[BryanCrotaz]

Is your suggestion to replace ember-collection with a new component?

[shaunc]

My new lazy-render component isn't quite ready yet. I patched through offset & limit to current eg-body, but now is even lazier than ever.