Fix segfault in ExtraNewLinesAfterCue.

Fixes issue #15

I've fixed the segfault in FileStructure.ExtraNewlinesAfterCue.
Problem was that it was trying to parse a cue on a new line with
nothing after it, so I've set it up to consume all the whitespace
after it's parsed cue settings or cue text.

This also seems to fix a lot of other tests.