Make region argument case insensitive

Re-opening PR 18 against working branch


Hi,

One for consideration. If you give -r lon, all you get back is 'Endpoint not found', which isn't very informative. 
So either the comparison can be case insensitive, or the error message can be a bit more descriptive.

I'd opt for case insensitive comparison, as ultimately the DNS lookup is case insensitive itself anyway.