Ensure "make test-node" runs against Node 0.10.30+

See #554. Nave is a userland way of switching between Node versions (think rvm). Targeting a specific Node version would help an eventual transition to any other version, and pin our tests against a specific API and its bugs.

Downsides: if Nave isn't permitted to cache Node versions in the manner it wants, it will re-download the Node binary each time the test is run.