add feature flags

We need the ability to load feature flags from a semi-versioned (major only or not at all), customizable url.

Something like this.

curl https://assets.osu.edu/virtual-assistant-covid/features/0.x/data.json
{
  "feature-option-1": "choice-x",
  "feature-boolean-2": true 
}

The path should probably be navigable locally and remote with a consistent set of rules.

../features/{MAJOR}.x/data.json