POST:
{ title: 'My Awesome T-shirt 2',
  description: 'All about the details. Of course it's black.',
  style: '12345' }
{ [MongoError: E11000 duplicate key error index: ecomm_database.products.$style_1  dup key: { : "12345" }]
  name: 'MongoError',
  err: 'E11000 duplicate key error index: ecomm_database.products.$style_1  dup key: { : "12345" }',

var Product = new Schema({
    title: { type: String, required: true },
    description: { type: String, required: true },
    style: { type: String, unique: true },
    modified: { type: Date, default: Date.now } });