title: Rails junction table name error
body: <p>I am trying to get a junction table working.
  I have three models: Professional, Skill and the cross reference table ProfessionalsSkills.</p>
  
  <p>The Professional model</p>
  
  <pre><code>class Professional &lt; ActiveRecord::Base
      has_many :professionals_skills
      has_many :skills, :through =&gt; :professionals_skills
  end
  </code></pre>
  
  <p>The Skill model</p>
  
  <pre><code>class Skill &lt; ActiveRecord::Base
      has_many :professionals_skills
      has_many :professionals, :through =&gt; :professionals_skills
  end
  </code></pre>
  
  <p>The cross reference table</p>
  
  <pre><code>class ProfessionalsSkills &lt; ActiveRecord::Base
      belongs_to :professional
      belongs_to :skill
  end
  </code></pre>
  
  <p>In Rails console</p>
  
  <pre><code>irb(main):005:0* @x = Professional.find(1)
    Professional Load (0.1ms)  SELECT  "professionals".* FROM "professionals"  WHERE "professionals"."id" = ? LIMIT 1  [["id", 1]]
  =&gt; #&lt;Professional id: 1, gender: 1, first_name: "Goofy", last_name: "Muff", date_of_birth: "1985-07-20 00:00:00", email_address: "example@example.com", city_id: 1, created_at: "2014-09-06 13:04:57", updated_at: "2014-09-06 13:04:57"&gt;
  irb(main):006:0&gt;
  </code></pre>
  
  <p>but... when I try:</p>
  
  <pre><code>@x.skills
  
  NameError: uninitialized constant Professional::ProfessionalsSkill
      from /Library/Ruby/Gems/2.0.0/gems/activerecord-4.1.5/lib/active_record/inheritance.rb:133:in `compute_type'
      from /Library/Ruby/Gems/2.0.0/gems/activerecord-4.1.5/lib/active_record/reflection.rb:221:in `klass'...
  </code></pre>
  
  <p>What am I doing wrong? I am using Rails 4.1.4</p>