Call endOfStream after the last segment has been buffered.

When the last segment in a playlist is appended, call `SourceBuffer.endOfStream()`. Fixes #111. Avoid using 1.10.3 of sinon.js. Make sure hitting play when a video ends restarts playback.
The sinon version is to work around a bug in the latest edition. You're right we need to get back onto mainline. There's no reason to use the patched version of 4.6.1 anymore.