Add benchmarks with other drivers (sqlite, pg) about vsql

[Terisback]

As soon as I find time, I'll do it.

[elliotchance]

On second thought, maybe just add the sqlite comparison as that's more apples to apples. Even though vsql can run as a postgresql server it's still a file on disk underneath and isn't used like a postgresql server would.

[elliotchance]

@Terisback do you feel like updating adding some makefile targets for bench-sqlite and bench-pg?

[dumblob]

I think both (sqlite & pg) would be useful despite each showing something different. A concurrency setup (i.e. on a machine with at least 4 CPUs/cores and an SSD disk) together with 100+ concurrent client connections would be best.