Allow names with uppercase letters in search box

[casey]

If you copy and paste something with uppercase letters in the search box on the homepage, or into /ordinal/NAME, it won't work because Ordinal::from_str currently only recognizes names with the lowercase letters a-z. We should think about accepting names with uppercase letters in them.

One downside of doing this is we can't use the uppercase letters for something else, because with this change it would be ambiguous whether or not they're a name.