title: ruby on rails 3 date attribute with date_select not being assigned
body: <p>I have a view with the following:</p>
  
  <pre><code>=f.date_select :start_date, { :start_year =&gt; 1990, :end_year =&gt; Time.now.year, :discard_day =&gt; true, :prompt =&gt; true, :order =&gt; [ :month, :year] }
  </code></pre>
  
  <p>Where my :start_year is an attribute on my ActiveRecord model called WorkHistory.
  And in my controller I have:</p>
  
  <pre><code>@work_history = WorkHistory.new(params[:work_history])
  </code></pre>
  
  <p>The start_date never gets set and is always <code>nil</code>. Am I missing something?</p>