Split WebVTTCueData from TTML/Empty CueData

Slight changes to tests (as Cue::Type became CueType, so the Cue::
prefix needed to disappear).
Hack to pass Cue tests on i386/-m32
Don't use doubles for time (fuzzy equality)
Merge pull request #19 from caitp/issue-19

Separate TTML and WebVTT Cue Data