Merge pull request #48 from jbottigliero/fix-ITokenResponse-type

fix: updates 'refresh_token' and 'refresh_expires_in' to be optional properties on the ITokenResponse

Author: bpedroza

src/ITokenResponse.ts

@@ -1,8 +1,8 @@
 export default interface ITokenResponse {
   access_token: string;
   expires_in: number;
-  refresh_expires_in: number;
-  refresh_token: string;
+  refresh_expires_in?: number;
+  refresh_token?: string;
   scope: string;
   token_type: string;
 }