Add `nesh-require` as a default plugin (See #11)

Lets you do things like

    .require http

which is the same as

    http = require('http')

Test Plan: built module, ran it, did `.require http`
Fixing tests

Test running was broken unrelated to the require plugin change.

With CoffeeScript 1.7, there was a change to the command line arguments
you need to give to Mocha

See: http://stackoverflow.com/questions/21431608/error-when-running-mocha-test-in-nodejs
Merge pull request #12 from ccheever/require-plugin

Add `nesh-require` as a default plugin (See #11). Fixes #11, #12.