Fuzzy benchmarks

**Issue by [kana-sama](https://github.com/kana-sama)**
_Tuesday Feb 28, 2017 at 17:04 GMT_
_Originally opened as https://github.com/BrianHicks/elm-benchmark/issues/7_

----

Calls of the same functions with the same arguments could be optimized by javascript engines and such benchmarks can't reveal some bottlenecks (f(5) - fast, f(6) - slow, f(7) - fast).

So imo it will be great to randomize arguments for any big iteration (50 times), like
```elm
fuzz2 : String -> (a -> b -> c) -> Generator a -> Generator b -> Benchmark
```

Of course there are some problems with `compare`, but I have some idea about stateful benchmarks (something like `fold`). And it's possible to realize `fuzz` above it with seed as state (I am reading the code right now).

Folds are basis for `map/filter/other` and they can be basis for benchmarks too :)