Add test for bwv77

The test fails for the offset=0.5, salami-sliced case. I'm very interested
to know whether this is because I input my "analysis" wrong; you see the
problem with the downbeat of the first measure (every voice has a quarter
note): in my analysis I write an event at offset 1.0 and an identical event
at offset 1.5, but the analyzer writes two identical events both at offset
1.0. Christopher?