Format 418 responses per the RFC

RFC 2324 specifies that the 418 error code conforms to "I'm a teapot",
with a lowercase letter T. This commit corrects the deficiency in the
current implementation, which featured an uppercase T.

Signed-off-by: Eugene E. Kashpureff Jr <eugene@khresear.ch>
Merge pull request #2 from KHresearch/master

Format 418 responses per the RFC