Basic es modules demo

[carsonfarmer]

This is a pretty simple demo/example of taking advantage of our new ES modules supports in all @textile/* libs. Here, an app in dev mode is used to create a basic HTML app that imports and existing "user" identity, and then authenticates with this user on the hub. It does not create any new data or threads on the hub, and any folks playing with the demo should use their own hub credentials and identities. Copies concepts from the user mailbox demo app.