Update README with info on measureStream-functions.
Update README with info on measureStream-functions.

Fixes #9.

mac-/node-statsd-client,msiebuhr/node-statsd-client,jmptrader/node-statsd-client,Raynos/node-statsd-client,uber/node-statsd-client,bolgovr/node-statsd-client,n-johnson/node-statsd-client