SciTools/iris — pull request #124 by esc24 (2012-10-03 10:05:10+00:00)
Title: Use of tuples for dimensions in coord to dim mapping

Modifications to cube.py so that the coord to dimensions mappings (```_aux_coords_and_dims``` and ```_dim_coords_and_dims```) now use tuples rather than lists. This should prevent inadvertent side effects. Cube.coord_dims() now returns a tuple of ints. ```cube.xml_element()``` explicitly converts to a list for xml output (there was a mix of tuples and lists before).