Added chai and mocha deps

run "npm install" to get em. Also added node_modules as gitignore

[wgreenberg/arbiter#1]
Added skeleton arbiter module and sanity check test

the test is totally temporary, just there to show that "npm test"
is wired up and that the arbiter module exists

[wgreenberg/arbiter#1]
Merge pull request #2 from wgreenberg/issues/1

Issues/1