Memory usage tests

Since there seems to be interest in improving memory usage, it'd be nice if there was repeatable benchmarks. This ports memory usage tests from Kefir to Coffee-Script. Additionally there is diamond-shaped stream and combineTemplate test cases.

Memory usage is measure before adding subscription, with subscription and after removing subscription. Ideally, memory usage after removing subscription should be the same as without subscription, but it seems that it isn't. This could indicate memory leaks, or just that V8 compiles code and it's seen in usage tests.