title: Module ''*'' has no exported member 'app'
body: <p>We are developing an open source app on ionic 2 platform, someone added Firebase to the project and I made pull request and now when I try to run the app I get this error. It is probably related to some of Firebase dependencies or packages. How can I fix this?</p>
  
  <p>Pretty much every line related to Firebase gives this error. For instance:</p>
  
  <pre><code>export declare function _getAuthBackend(app: firebase.app.App): FirebaseSdkAuthBackend;
  </code></pre>
  
  <p>here is the code:</p>
  
  <pre><code>import * as firebase from 'firebase';
  import { Observable } from 'rxjs/Observable';
  export declare abstract class AuthBackend {
      abstract authWithCustomToken(token: string): Promise&lt;FirebaseAuthState&gt;;
      abstract authAnonymously(options?: any): Promise&lt;FirebaseAuthState&gt;;
      abstract authWithPassword(credentials: EmailPasswordCredentials): Promise&lt;FirebaseAuthState&gt;;
      abstract authWithOAuthPopup(provider: AuthProviders, options?: any): Promise&lt;firebase.auth.UserCredential&gt;;
      abstract authWithOAuthRedirect(provider: AuthProviders, options?: any): Promise&lt;void&gt;;
      abstract authWithOAuthToken(credentialsObj: firebase.auth.AuthCredential, options?: any): Promise&lt;FirebaseAuthState&gt;;
      abstract onAuth(): Observable&lt;FirebaseAuthState&gt;;
      abstract getAuth(): FirebaseAuthState;
      abstract unauth(): Promise&lt;void&gt;;
      abstract createUser(credentials: EmailPasswordCredentials): Promise&lt;FirebaseAuthState&gt;;
      abstract getRedirectResult(): Observable&lt;firebase.auth.UserCredential&gt;;
  }
  export declare enum AuthProviders {
      Github = 0,
      Twitter = 1,
      Facebook = 2,
      Google = 3,
      Password = 4,
      Anonymous = 5,
      Custom = 6,
  }
  export declare enum AuthMethods {
      Popup = 0,
      Redirect = 1,
      Anonymous = 2,
      Password = 3,
      OAuthToken = 4,
      CustomToken = 5,
  }
  export interface AuthConfiguration {
      method?: AuthMethods;
      provider?: AuthProviders;
      scope?: string[];
  }
  export interface FirebaseAuthState {
      uid: string;
      provider: AuthProviders;
      auth: firebase.User;
      expires?: number;
      github?: firebase.UserInfo;
      google?: firebase.UserInfo;
      twitter?: firebase.UserInfo;
      facebook?: firebase.UserInfo;
      anonymous?: boolean;
  }
  export declare function authDataToAuthState(authData: firebase.User, providerData?: firebase.UserInfo): FirebaseAuthState;
  export declare function stripProviderId(providerId: string): string;
  export interface EmailPasswordCredentials {
      email: string;
      password: string;
  }
  </code></pre>