add sync-to-downbeat function to track

As per @enedrio's idea, it would be cool if one track could be synced to the downbeat of another.

What is the name of this function?

• dsync for "downbeat sync"?
• syncd for "sync to downbeat"?
• downbeat?

I imagine that the track doing the calling is looking to by synced to the track passed into it. Or should it be the other way around? E.g.

t1 = new track()
t2 = new track()
t1.beat(2), t2.beat(7)
// some time passes...
t1.syncd(t2) // <--------- what should happen?

yaaaaaaas, this

@hughrawlinson what do you think about the question I am posing? From which direction should the syncing happen?

I mean, if the first track that starts established a global pattern that everything would sync to, that'd be real nice, otherwise just a pattern for doing that sort of thing would be good. Otherwise, definitely t1 should sync to t2 because you're calling the function (and semantically mutating) t1.