New idea: only linearly interpolate between two consecutive "record"
messages. I don't know what else to do. My FIT files have all sorts
of weirdness I can't explain. One, for example, has two consecutive
start events with the same timestamp. What does that mean?
This is all proof that just having the file "format" isn't really
enough. What you need is the file *semantics*, and we don't have that
for FIT yet.
I'm not really sure what these are doing in the FIT file Jamie sent
to the list, but there's only one of them, and it's at the end of a
long rest period, so it seems safe to ignore it for now.
