Rendering long CTLs is slow as hell

[passy]

trafficstars

Rendering the Tweets takes a considerable amount of time, in particular when dragging Tweets around. That was to be expected since there are no optimizations whatsoever. I should enable pure rendering (https://github.com/facebook/react/blob/master/src/addons/ReactComponentWithPureRenderMixin.js) and proper batching (https://github.com/facebook/react/blob/8a47813baabcb200f5e0a496dd959cb0ef3adcf3/src/core/ReactDefaultBatchingStrategy.js).