fix 'selects a playlist after segment downloads'
fix 'moves to next segment if network error'
Revert "fix 'selects a playlist after segment downloads'"

This reverts commit 3bccfa73915d1a547367b05aa317565d7d0c7535.
make sure that options is an object
Use sinon fakeXmlHttpRequest.
Change out the custom synchronous XHR to use sinon's fake XHR.
This allows to decide exactly when to respond to XHRs.