Mixed-case paths broken in domain-mapping directives

```
When DomainLawyer was written we could only work with Origins -- we couldn't 
authorize or map to subpaths.  So lower-casing the whole URL prefix was fine.

However now we support sub-paths in domain-mapping commands and I think we 
lower-case them, so mixed-case ones won't match.

```

Original issue reported on code.google.com by `jmara...@google.com` on 9 May 2013 at 11:54
