Empty page by runinng app.py

Following [Running without Docker](https://github.com/allenai/lm-explorer#running-without-docker), I got empty page after running`python app.py --port 8000 --dev` and access to `localhost:8000`.

It seems ok, but I have no idea why I got empty page.
```
INFO:werkzeug:127.0.0.1 - - [15/Apr/2020 22:11:20] "GET / HTTP/1.1" 200 -
```
#20 was caused by version of styled-components, thus I fixed styled-components to latest version([5.1.0](https://cdnjs.com/libraries/styled-components)) but it failed.