code: def vizier(cat,filePath,ReadMePath,
             catalogname='catalog.dat',readmename='ReadMe'):
      
      _download_file_vizier(cat,filePath,catalogname=catalogname)
      _download_file_vizier(cat,ReadMePath,catalogname=readmename)
      return None
docs: NAME:
         vizier
      PURPOSE:
         download a catalog and its associated ReadMe from Vizier
      INPUT:
         cat - name of the catalog (e.g., 'III/272' for RAVE, or J/A+A/... for journal-specific catalogs)
         filePath - path of the file where you want to store the catalog (note: you need to keep the name of the file the same as the catalogname to be able to read the file with astropy.io.ascii)
         ReadMePath - path of the file where you want to store the ReadMe file
         catalogname= (catalog.dat) name of the catalog on the Vizier server
         readmename= (ReadMe) name of the ReadMe file on the Vizier server
      OUTPUT:
         (nothing, just downloads)
      HISTORY:
         2016-09-12 - Written - Bovy (UofT)