Parallel loading of segments

[gsimko]

Based on segment-loader.js (function load) it looks like the segment loader buffers one segment at a time. This is suboptimal if the video server has high latency, as concurrently reading multiple segments would decrease the chance of stalls.

It looks easy to update segment-loader to do so, but I don't feel confident that it would not break the logic. Can someone who is more familiar with http-streaming comment whether it's a feasible change?