[iban] Support require/import style

iban/iban.d.ts

@@ -55,4 +55,8 @@ interface IBANStatic {
     toBBAN(iban: string, separator: string[]): string;
 }
 
-declare var IBAN: IBANStatic;
+declare var IBAN: IBANStatic;
+
+declare module 'iban' {
+  export = IBAN;
+}