title: <django.db.models.fields.related.RelatedManager object at 0x7ff4e003d1d0> is not JSON serializable
body: <p>I'm getting the following traceback on a reverse relationship - </p>
  
  <pre><code>Traceback:
  File "/opt/common/external/python_modules/django/core/handlers/base.py" in get_response
    164.                 response = response.render()
  File "/opt/common/external/python_modules/django/template/response.py" in render
    158.             self.content = self.rendered_content
  File "/opt/common/external/python_modules/rest_framework/response.py" in rendered_content
    71.         ret = renderer.render(self.data, media_type, context)
  File "/opt/common/external/python_modules/rest_framework/renderers.py" in render
    674.         context = self.get_context(data, accepted_media_type, renderer_context)
  File "/opt/common/external/python_modules/rest_framework/renderers.py" in get_context
    635.             'content': self.get_content(renderer, data, accepted_media_type, renderer_context),
  File "/opt/common/external/python_modules/rest_framework/renderers.py" in get_content
    397.         content = renderer.render(data, accepted_media_type, renderer_context)
  File "/opt/common/external/python_modules/rest_framework/renderers.py" in render
    103.             separators=separators
  File "/opt/common/external/anaconda/2.3.0/lib/python2.7/json/__init__.py" in dumps
    250.         sort_keys=sort_keys, **kw).encode(obj)
  File "/opt/common/external/anaconda/2.3.0/lib/python2.7/json/encoder.py" in encode
    209.             chunks = list(chunks)
  File "/opt/common/external/anaconda/2.3.0/lib/python2.7/json/encoder.py" in _iterencode
    431.             for chunk in _iterencode_list(o, _current_indent_level):
  File "/opt/common/external/anaconda/2.3.0/lib/python2.7/json/encoder.py" in _iterencode_list
    332.                 for chunk in chunks:
  File "/opt/common/external/anaconda/2.3.0/lib/python2.7/json/encoder.py" in _iterencode_dict
    408.                 for chunk in chunks:
  File "/opt/common/external/anaconda/2.3.0/lib/python2.7/json/encoder.py" in _iterencode
    442.             o = _default(o)
  File "/opt/common/external/python_modules/rest_framework/utils/encoders.py" in default
    64.         return super(JSONEncoder, self).default(obj)
  File "/opt/common/external/anaconda/2.3.0/lib/python2.7/json/encoder.py" in default
    184.         raise TypeError(repr(o) + " is not JSON serializable")
  
  Exception Type: TypeError at /api/servers/
  Exception Value: &lt;django.db.models.fields.related.RelatedManager object at 0x7f5bfe876990&gt; is not JSON serializable
  </code></pre>
  
  <p>Serializer</p>
  
  <pre><code>class TblserversSerializer(serializers.ModelSerializer):
      bmccode = serializers.SerializerMethodField('get_bmc')
  
      def get_bmc(self, obj):
          code = Tblbmcgroups.objects.filter(groupid = obj.recordownerid).values_list('bmccode')[0][0]
          return code
  
      class Meta:
          model = Tblservers
          fields = ('serverid', 'servername', 'isvirtual', 'locationid', 'managedbyid', 'operatingsystem', 'model',
                    'assettag', 'inceptiondate', 'comments', 'assetstatusid', 'recordownerid', 'lastmodifieddate',
                    'lastmodifiedby', 'bmccode', 'server_applicationlinks')
          depth = 1
  </code></pre>
  
  <p>Models</p>
  
  <pre><code>class Tblvmserverlinks(models.Model):
      id = models.IntegerField(db_column='ID', primary_key=True) # Field name made lowercase.
      virtualserverid = models.IntegerField(db_column='virtualServerId') # Field name made lowercase.
      underlyingserverid = models.IntegerField(db_column='underlyingServerId') # Field name made lowercase.
      comments = models.TextField(blank=True)
      lastmodifieddate = models.DateTimeField(db_column='lastModifiedDate', blank=True, null=True) # Field name made lowercase.
      lastmodifiedby = models.CharField(db_column='lastModifiedBy', max_length=255, blank=True) # Field name made lowercase.
  #    upsize_ts = models.TextField(blank=True) # This field type is a guess.
      class Meta:
          managed = False
          db_table = 'tblVMServerLinks'
  
  class Tblapplicationserverlinks(models.Model):
      id = models.AutoField(db_column='ID', primary_key=True) # Field name made lowercase.
      applicationid = models.ForeignKey('Tblapplications', db_column='applicationId', related_name='application_serverlinks') # Field name made lowercase.
      serverid = models.ForeignKey('Tblservers', db_column='serverId', related_name='server_applicationlinks') # Field name made lowercase.
      environmentid = models.IntegerField(db_column='environmentId') # Field name made lowercase.
      comments = models.TextField(blank=True)
      lastmodifieddate = models.DateTimeField(db_column='lastModifiedDate', blank=True, null=True) # Field name made lowercase.
      lastmodifiedby = models.CharField(db_column='lastModifiedBy', max_length=255, blank=True) # Field name made lowercase.
  #    upsize_ts = models.TextField(blank=True) # This field type is a guess.
      class Meta:
          managed = False
          db_table = 'tblApplicationServerLinks'
  </code></pre>
  
  <p>view</p>
  
  <pre><code>class TblserversViewSet(viewsets.ModelViewSet):
      """
      API endpoint that allows users to be viewed or edited.
      """
      queryset = Tblservers.objects.all()
      serializer_class = TblserversSerializer
      filter_class = TblserversFilter
  </code></pre>