Fix issue with event 7632

Event 7632 is a CSV file that ends with a line 'NOCLAS,-1'.  There are
no competitors in this class, so it would seem a bit harsh to reject the
file when this section can easily be ignored.  We'll still check for
non-negative control counts, but only if there are any competitors in
the class.
Fix handling of zero splits in CSV data

Split times of 00:00 in SplitsBrowser CSV files indicate that there is
no time to the given control, not that the split is 0 seconds.

Fixes #28.
Remove Competitor.fromSplitTimes

This function is now only used by tests, so it has been moved to
test-support.js.
Interpret zero start times as missing
Ignore additional controls in IOF XML v3.0

I happened to notice that the IOF XML v3.0 format supports additional
controls.  Split times at such controls weren't being ignored when they
should have been.

IOF XML v2.0.3 appears not to support such controls.
Update version number and generated JS files