add flatMap perf test
add test for #353
fix flatMapLatest/combine glitch. Dep cache defeated
restore dep caching with transaction scope and invalidation
Some performance shaving
update relnotes
release 0.7.16
extract DepCache from UpdateBarrier
Bacon.sampledBy() implementation with few tests
add more tests for Bacon.sampledBy()
laziness in Bacon.sampledBy()
add Bacon.sampledBy() perf test
WIP (I'll cleanup commit history at the end)
fix issue with properties as samplers in `Bacon.sampledBy()`
remove commented out code