Change path of static file

[enzofrnt]

Related to #141 with the change that have been asked for.

Change path of static file to something more logic :
Before :

─ static/django_eventstream
    ├── ReconnectingEventSource.min.js.map
    ├── browsable-api-eventstream.css
    ├── browsable-api-eventstream.js
    ├── eventsource.min.js
    ├── json2.js
    └── reconnecting-eventsource.js

After :

─ static/django_eventstream
    ├ css
    | └── browsable-api-eventstream.css
    ├ html
    └ js
      ├── ReconnectingEventSource.min.js.map
      ├── browsable-api-eventstream.js
      ├── eventsource.min.js
      ├── json2.js
      └── reconnecting-eventsource.js