[Dev] Web interface for model interaction

To start with, this should be a basic single-page application served by Flask, and backed by a [FlaskRESTful](https://flask-restful.readthedocs.io/en/latest/) API to serve the model and track user session state.

The single-page app can be done with any JS UI framework, or just vanilla JS + JQuery.

Primary features:

1. Input textbox for typing commands, dialog utterances, and narrative passages.
2. Output textbox for seeing results of model interaction
3. Support for additional conditioning prompt to precede the active dialog context
4. Support for speech-to-text and text-to-speech via public API

Some inspiration: https://ricsinaruto.github.io/chatbot.html
More inspiration: https://github.com/AbrahamSanders/seq2seq-chatbot/blob/master/seq2seq-chatbot/chat_ui.html