text: Title: Parsing Dash initial_arguments broken in v1.6.1
  Body: I've identified a regression in release 1.6.1 that causes a bug when parsing `initial_arguments` as a serialized string.
  
  We have an app that uses `initial_arguments` as follows. The `dash_initial_arguments` is a *string* of serialized JSON that is generated via `views.py` and passed to the Django template via `context`.
  
  ```
  {% plotly_app name="MyApp" ratio=1 initial_arguments=dash_initial_arguments %}
  ```
  
  Prior to v1.6.1, this worked as intended. However, there was a [change to dash_wrapper.py](https://github.com/GibbsConsulting/django-plotly-dash/compare/v1.6.0...v1.6.1#diff-7b3d671859d84ee8816d9e86a0705b5e13e3f3b49dc12a2a6aa4caa7a290f89aR466) in v1.6.1 that removed the JSON deserialization logic. Specifically, this change occurred in https://github.com/GibbsConsulting/django-plotly-dash/commit/cddf57559a8dcd12d1cdbb42d95c48b29678ee11.
  
  ![Screen Shot 2021-03-15 at 2 02 17 PM](https://user-images.githubusercontent.com/10052880/111200745-6d49ac00-8598-11eb-8290-6d700b578544.png)
  
  `initial_arguments` is still a string, but since the parsing has been removed, this now results in the following error:
  
  ```
  ValueError: dictionary update sequence element #0 has length 1; 2 is required
  ```
  
  @sdementen or @sebastiendementen do you have any context for why this parsing logic was removed?