dgeni: @deprecated tag has no visible output in API docs

[naomiblack]

See https://angular.io/docs/ts/latest/api/common/FORM_BINDINGS-let.html for an example of a live page that should have an @deprecated warning, per https://github.com/angular/angular/blob/2.0.0-beta.15/modules/angular2/src/common/forms.ts#L64-L64

@ericjim @IgorMinar @petebacondarwin

[ericjim]

I'll do this one next, I'll refer to the API doc proposal from here #964

[ericjim]

Work in-progress, but getting there.

[ericjim]

@naomiblack as it stands, I am defaulting to stable.

I can perform a check for @stable, however, if we choose to default to experimental every single page in the api doc will have an experimental label, unless given that the explicit @stable which currently does not exist in angular.io or angular2. I can add the tag in angular.io, but we will need to coordinate the @stable effort on angular2. Is this what we want?

References:
#1098

Preview:

[naomiblack]

on further reflection, I think we need to have four states: stable / experimental / deprecated / undefined.

Could you create both @stable and @experimental and then make the default (undefined) show no button at all? that gives us space to go through the API surface incrementally, and saves us from accidentally making something experimental look "done".

@IgorMinar FYI