Rename `models.json` to `model-config.json`

The name `models.json` was potentially confusing since there are no
models defined in that file.
Merge pull request #19 from strongloop/feature/rename-models-to-models-config

Rename `models.json` to `model-config.json`
v2.0.0-beta2
Merge branch 'release/2.0.0-beta2' into production