Differentiate between microbenchmarks and macrobenchmarks

[dhil]

We should classify the current set of benchmarks as microbenchmarks. They don't really resemble any "real-world" workload. In addition, we should introduce a notion of macrobenchmarks, which are supposed to resemble real-world workloads. One example of a macrobenchmark is a httpserver.

[jasigal]

@dhil @codrutiftode and I had a chat, and Codrin decided that bringing in some HTTP server benchmarks would be good goal