Fixed the "twenties" in SpanishNumberToWordsConverter

The twenties in letters were incorrect in Spanish. Example: it is not "veinte cinco" it is "veinticinco"

Source: http://es.wikipedia.org/wiki/Anexo:Nombres_de_los_n%C3%BAmeros_en_espa%C3%B1ol

@thunsaker, @bangoker, @juan-hawa