title: Problems to search ActsAsTaggableOn with sunspot
body: <p>I've setup sunspot and I'm searching fine in my <code>Place.name</code> field</p>
  
  <p>Now I want to search by "acts as taggable" tags</p>
  
  <p>I've setup two contexts to taggable, categories</p>
  
  <p>with this model and controller I'm not getting any errors but when I search for my tag name sunspot doesn't return any results.</p>
  
  <p>I've run <code>rake sunspot:reindex</code> and <code>rake sunspot:solr:reindex</code> but no change.</p>
  
  <p>When I run <code>Place.last.categories</code> in rails console I only get one array <code>["Category one","Category 2"]</code></p>
  
  <p>Model</p>
  
  <pre><code>class Place &lt; ActiveRecord::Base
    extend FriendlyId
    friendly_id :name, use: :slugged
  
    searchable :auto_index =&gt; true, :auto_remove =&gt; true  do
      text :name, :stored =&gt; true
      string :category_list, :multiple =&gt; true, :stored =&gt; true
    end
  
  
    acts_as_votable   
    acts_as_mappable :default_units =&gt; :kms,
                     :lat_column_name =&gt; :latitude,
                     :lng_column_name =&gt; :longitude
  
  
    validates_presence_of :name , :state, :city, :neighborhood, :adress,:latitude, :longitude
  
    belongs_to :user
  
    acts_as_ordered_taggable_on :categories, :obstacles
  
  
  
  end
  </code></pre>
  
  <p>Controller</p>
  
  <pre><code>class PlacesController &lt; ApplicationController
    before_action :set_place, only: [:show, :edit, :update, :destroy, :upvote, :downvote, :favorite]
    before_action :authenticate_user!, except: [:index, :show]
  
    # GET /places
    # GET /places.json
    def index
      @search = Place.search do
        fulltext params[:search]
      end  
      @places = @search.results
    end
  </code></pre>