to_xml and read_xml
http://stackoverflow.com/questions/18574108/how-do-convert-a-pandas-dataframe-to-xml
cc @jreback

I don't _think_ there is a standard xml, but perhaps his could be generalised? If not maybe simply adding this recipe to the cookbook is useful.

Solutions for read_xml are hacking tree with from_records
 http://stackoverflow.com/a/10948591/1240268
or just as a list http://stackoverflow.com/a/16993660/1240268

too much of a dark art to generalise?
