title: undefined method `symbolize_keys' when using factory girl traits
body: <p>I'm using ruby v1.9.3 and factory_girl v2.2  and trying to setup traits.  But am getting this error when I try to use my trait. Is it because of the ruby version I am using?</p>
  
  <pre><code> Failure/Error: let!(:notification) { create(:notification, :confirmable) }
   NoMethodError:
     undefined method `symbolize_keys' for :confirmable:Symbol
   # ./spec/controllers/api/v1/sms_controller_spec.rb:13:in `block (3 levels) in &lt;top (required)&gt;
  </code></pre>
  
  <p>This is my factory:</p>
  
  <pre><code>FactoryGirl.define do
    factory :notification do
      smssid { Faker::Number.number(10) }
      msg    { Faker::Lorem.sentence(3) }
      to     { Faker::PhoneNumber.phone_number }
  
      trait :confirmable do
        confirmable  "true"
      end
    end
  end
  </code></pre>
  
  <p>spec:</p>
  
  <pre><code>require 'spec_helper'
  
  describe Api::V1::SmsController do
  
    let!(:user) { create(:user) }
  
    describe "GET /api/v1/user/sms" do
  
      let!(:notification) { FactoryGirl.create(:notification, :confirmable) }
  
      context "a user replies to a confirmation with c" do
        it "does something" do
          get :incomming_message, :sid =&gt; notification.smssid,
                                  :to =&gt; notification.to,
                                  :from =&gt; user.phone_number,
                                  :body =&gt; "c",
                                  :status =&gt; "recieved",
                                  :format =&gt; :json
          notification.reload
          notification.confirmed.should eq(true)
        end
      end
    end
  end
  </code></pre>
  
  <p>*** Edit, updated with my spec file</p>