Add some test coverage for server id mapping.
Work around a platform issue with XHRs and app:// URLs; if the file isn't found, send() currently throws.
Add a comment about our XHR workaround for app:// URLs
Merge pull request #110 from mozsquib/autoconfig-xhr-workaround

Work around a platform issue with XHRs and app:// URLs
Merge pull request #108 from asutherland/serverid-map

Add some test coverage for server id mapping. r=squib, a=blocking-basecamp