remove benchmarks from npm test

[jonathanong]

this makes running npm test unnecessarily long

[lovell]

Thanks Jonathan. If it's OK with you, I'd like to add a few more functional tests before doing this as the perf tests are currently providing some of that coverage (sadface, I know).

[jonathanong]

sounds good to me! would also be nice if you used a test framework like mocha so you could have pretty outputs