title: adding index to email column culprit for unit tests failing
body: <p>I am new to devise and rails and I just integrated devise with my sample app. What I noticed is after creating a <em>user</em> model, all my unit tests were failing. I went to try to narrow this and found that even the generated assert 'the truth' one for <code>user_test.rb</code> also fails:</p>
  
  <pre><code>ActiveRecord::RecordNotUnique: SQLite3::ConstraintException: \
      column email is not unique: INSERT INTO "users" (...
  </code></pre>
  
  <p>Once I commented out the <code>add_index</code> ...</p>
  
  <pre><code># add_index :users, :email, :unique =&gt; true
  </code></pre>
  
  <p>... and re-ran <code>rake db:test:load</code> and re-run tests with <code>ruby -I test test/unit/user_test.rb</code> it passes.</p>
  
  <p>Has anyone else experience this?</p>