text: Title: Application does not work when I upload photos to an eve dict schema properties
  Body: Hi:
  
  I have an eve schema set up as such:
  
  ``` python
  'schema': {
          'email': {
              'type': 'string',
              'unique': True,
          },
          'isEmailVerified': {
              'type': 'boolean',
              'default': False,
              'readonly': True,
          },
          'profile': {
              'type': 'dict',
              'schema': {
                  'avatar': {
                      'type': 'media',
                  },
                  'bio': {
                      'type': 'string',
                      'minlength': 1,
                      'maxlength': 30,
                  },
                  'location': {
                      'type': 'dict',
                      'schema': {
                          'state': {
                              'type': 'string',
                          },
                          'city': {
                              'type': 'string',
                          },
                      },
                  },
                  'birth': {
                      'type': 'datetime',
                  },
                  'gender': {
                      'type': 'string',
                      'allowed': ["male", "famale"],
                  }
              },
          },
      }
  ```
  And I'm using cURL to make a PATCH request:
  
  ```cURL
  curl -X PATCH "http://127.0.0.1:5000/api/v1/accounts/5a461646b2fcb841401ea437" -H 'If-Match: a1944717f279751875f6f6794147b258df7e2af1' -F "profile.avatar=@WechatIMG21.jpeg"
  ```
  Application is not responding and blocking other requests. How can I upload the photo?