Remove reference to `this`

[simonexmachina]

Remove reference to this so that Faker.Internet.email and domainName can be used without having to bind the function receiver with Faker.Internet.email.bind(Faker.Internet).

Before:

var factory = require('factory-girl'),
    User = require('src/models/User');
factory.define('User', User, {
  given_name: Faker.Name.firstName,
  surname: Faker.Name.lastName,
  email: Faker.Internet.email.bind(Faker.Internet)
});

After:

var factory = require('factory-girl'),
    User = require('src/models/User');
factory.define('User', User, {
  given_name: Faker.Name.firstName,
  surname: Faker.Name.lastName,
  email: Faker.Internet.email
});

[simonexmachina]

It's not clear how to run the build step, so I haven't done anything with that.

[simonexmachina]

Closing this PR, not sure why I forked this repo rather than Marak's