Cue sheet parser rounds indexes to nearest second

When playing a track from a long file using a cue sheet, track starts at a round number of seconds, not at the exact frame of the index from the cue sheet. This is annoying when there is no silent gap between tracks.

For my own use, I have removed the math.floor() calls from cue.lua, which seems to work with flac files on Windows and Ubuntu, but I don't know why the times were rounded down or whether using floats for times will cause other problems. :start-time= seems to support float, maybe it didn't in older versions?