Boyscout HTTP Helper specs

Remove OpenStructs
Ensure HttpHelper handles 204 - No Content

204 - No Content is expected to come from requests
for full hashes on hash prefixes which have been
deleted from the database since the client last
updated. When prefixes match, but full hash
requests return 204. The URL should be treated as
a non-hit.
Return nil for 204 - No Content responses
Merge pull request #16 from mobiledefense/issues/16-try-to-split-no-response

Lookup certain domains raises NoMethodError: undefined method `split' for nil:NilClass