title: Rails Submit Button doesn't do anything on click after nested form added
body: <p>I'm trying to use a nested form at the moment to add category tags to a song as you create the song. The form was working fine until I added the nested attributes to it, and now the submit button doesn't do anything when you click on it (the page doesn't reload or anything). </p>
  
  <p>In my model a song has many categories though categorizations, and vice versa.</p>
  
  <p>Here's the form:</p>
  
  <pre><code>  &lt;div class="span10 offset1"&gt;
      &lt;%= form_for(@song) do |f| %&gt;
  
        &lt;%= f.label :title, "Title" %&gt;
        &lt;%= f.text_field :title %&gt;
  
        &lt;%= nested_form_for(@song.categorizations.build) do |f| %&gt;
          &lt;%= f.label :category_id, "TAG" %&gt;
          &lt;%= f.select :category_id, options_for_select(Category.all.collect {|c| [ c.tag, c.id ] }, { :include_blank =&gt; true }), prompt: "" %&gt;
        &lt;%end%&gt;
  
        &lt;%= f.submit "Save song", class: "btn btn-large btn-primary" %&gt;
      &lt;% end %&gt;
    &lt;/div&gt; 
  </code></pre>
  
  <p>And my controller for songs:</p>
  
  <pre><code>  def new
      @song = Song.new
    end
  
   def create
      @song = Song.new(params[:song])
      if @song.save
  
          flash[:success] = "Song successfully added to library"
          redirect_to @song
      else
          #FAIL!
          render 'new'
      end
    end
  </code></pre>
  
  <p>The Categorization controller:</p>
  
  <pre><code>def new
      @categorization = Categorization.new
    end
  
    def create
      @song = Song.find(params[:id])
      @categorization = Category.new(params[:categorization])
      if @categorization.save
          flash[:success] = "Tag added!"
          redirect_to song_path(@song)
      else
          flash[:fail] = "TAG ERROR"
          redirect_to edit_song_path(@song)
      end
    end
  </code></pre>
  
  <p>Thank you in advance for any help!</p>