Find some way not to hardcode version list

[Gaurav0]

const EMBER_VERSIONS = ['2.4.4', '2.3.2', '2.2.2', '2.1.2', '2.0.3', '1.13.13', '1.12.2'];
const EMBER_DATA_VERSIONS = ['2.4.3', '2.3.3', '2.2.1', '2.1.0', '2.0.1', '1.13.15'];

It would be nice if we can get this list from somewhere?

[rwjblue]

We already have some bit of fixture data that we maintain when we do Ember releases (here), I think we should create a better process around this.

@chancancode - What do you think?

[GCheung55]

I agree it would be nice to not have a hardcoded versions list.

Some ideas I have off the top are:

1. At build time, read from npm/yarn info on ember versions available and make the data available via `config/environment.js. This solution depends on a deployment every time. Maybe a web hook listening for new versions of ember-source and ember-data?
2. Periodically write to a file the versions available and have ember-twiddle read from that file at run time. This solution may not require a deployment of ember-twiddle every time but would depend on a web hook to listen for new versions of ember-source and ember-data in order to write a new file and upload it.