title: bookshelf.js not loading relation
body: <p>Im new to bookshelfjs and i want to get the data from other table using the ID from other table.
  Im using this sample data:</p>
  
  <pre><code>/* User's Table */
  ----------------+-------------------+----------
     lastname     |    firstname      |   id  
  ----------------+-------------------+---------
  Dela Cruz          Juan                1
  Pendoku            Pedro               2
  
  /* Logs's Table */
  ----------------+--------------+----------
       userid     |    time      |   id  
  ----------------+--------------+---------
    1                 8:00           1
    2                12:00           2
    1                 9:00           3
  </code></pre>
  
  <p>Question: how i can query the logs of specific user thru bookshelf.js?</p>
  
  <p>so the result should be like this:</p>
  
  <pre><code>----------------+--------------+----------
       lastname   |    time      |   id  
  ----------------+--------------+---------
   Dela Cruz          8:00           1
   Dela Cruz          9:00           3
  </code></pre>
  
  <p>My query:</p>
  
  <pre><code>new User({'lastname': 'Dela Cruz'})
    .logs()
    .fetch()
    .then(function(timelog) {
      console.log(timelog.toJSON());
  }); 
  </code></pre>
  
  <p>My models</p>
  
  <pre><code>var User, Log;
  
  User = bookshelf.Model.extend({
    tableName:'user',
    logs: function() {
       return this.hasMany(Log, 'userid');
    }
  });
  
  Log = bookshelf.Model.extend({
    tableName:'log',
    user: function(){
      return this.belongsTo(User, 'userid');
    }
  });
  </code></pre>
  
  <p>Log Error:</p>
  
  <pre><code>{ __cid: '__cid1',
    method: 'select',
    options: undefined,
    bindings: [undefined],
    sql: 'select log.* from log where log.userid = ?'
  }
  </code></pre>