Get attributes of a NetCDF file
        
        :return {type:dict} outStr: Attribute structure.
        :author: Renaud Dussurget

def attributes(self, filename, **kwargs):
        """
        Get attributes of a NetCDF file
        
        :return {type:dict} outStr: Attribute structure.
        :author: Renaud Dussurget
        """
        
        #Open file
        self._filename = filename
        ncf = ncfile(self._filename, "r")
     
        #Get list of recorded parameters:
        keys = ncf.__dict__.keys()
        outStr = OrderedDict()
        for a in keys: outStr.update({a:ncf.__getattr__(a)})

        return outStr