allow apps to supply custom reason phrases for HTTP response codes

Allow applications to return:

{halt, {Code::integer(), ReasonPhrase::iolist()}}

in order to provide custom reason phrases in their responses. The original
{halt, Code} also still works.
add doc directory to .gitignore
Merge pull request #141 from basho/custom-reason-phrase

merge support for custom reason phrases for HTTP response codes
Flush body when DELETE to keep alive connection

DELETE may have body and mochiweb will close socket because it's unsafe
to keep alive with remaining bytes.
Flush body after resource call so that resource module can handle body.
Merge pull request #142 from basho/ss-throw-body-away-when-delete

Read body when DELETE to keep alive connection
fix wrq:response_code/1 to handle custom reason phrase

An attempt to use webmachine tracing crashed due to the wrq:response_code/1
function not handling custom reason phrases introduced in commit
dedc5736. Add a new clause for that function to handle custom reason
phrases.
handle custom reason phrases as iolist() in make_code

Treat custom reason phrases as the iolist() type, not iodata(), in
webmachine_request:make_code/1, as per the documentation.
Merge pull request #147 from basho/sbv-fix-respcode

fix wrq:response_code/1 to handle custom reason phrase, and handle custom reason phrases as iolist() in make_code