feat(typings): Output actions should extend input actions.

After some discussion, it was agreed that essentially all actions flow through input actions including output actions. This means that output actions should indeed extend from input actions.

index.d.ts

@@ -38,11 +38,11 @@ export declare class StateObservable<S> extends Observable<S> {
 }
 
 
-export declare interface Epic<T extends Action, O extends Action = T, S = void, D = any> {
+export declare interface Epic<T extends Action, O extends T, S = void, D = any> {
   (action$: ActionsObservable<T>, state$: StateObservable<S>, dependencies: D): Observable<O>;
 }
 
-export interface EpicMiddleware<T extends Action, O extends Action = T, S = void, D = any> extends Middleware {
+export interface EpicMiddleware<T extends Action, O extends T, S = void, D = any> extends Middleware {
   replaceEpic(nextEpic: Epic<T, O, S, D>): void;
 }
 
@@ -56,9 +56,9 @@ interface Options<D = any> {
   dependencies?: D;
 }
 
-export declare function createEpicMiddleware<T extends Action, O extends Action = T, S = void, D = any>(rootEpic: Epic<T, O, S, D>, options?: Options<D>): EpicMiddleware<T, O, S, D>;
+export declare function createEpicMiddleware<T extends Action, O extends T, S = void, D = any>(rootEpic: Epic<T, O, S, D>, options?: Options<D>): EpicMiddleware<T, O, S, D>;
 
-export declare function combineEpics<T extends Action, O extends Action = T, S = void, D = any>(...epics: Epic<T, O, S, D>[]): Epic<T, O, S, D>;
+export declare function combineEpics<T extends Action, O extends T, S = void, D = any>(...epics: Epic<T, O, S, D>[]): Epic<T, O, S, D>;
 export declare function combineEpics<E>(...epics: E[]): E;
 export declare function combineEpics(...epics: any[]): any;