*

  constructor(repo: Microcosm, scope: Object) {
    super()

    this.repo = repo
    this.scope = scope
    this.bindings = {}
    this.subscriptions = {}
    this.value = {}
    this.revision = 0

    this.repo.on('change', this.compute, this)
  }
@fileoverview A general modelling class used by the Presenter's
getModel function.
@flow