When using the node/npm selenium-webdriver module to wrap mocha the wrapped versions
of beforeEach/it/afterEach/etc. do not correctly maintain the `this` value inside the
tests (which is normally a convenient place to share per test data before before/after
hooks and the test).

Fixing this seems to require add a bind call to https://github.com/SeleniumHQ/selenium/blob/master/javascript/node/selenium-webdriver/testing/index.js#L123

Changing the line from:
flow.execute(fn).then(seal(done), done);

To:
flow.execute(fn.bind(this)).then(seal(done), done);