check only the body_state

this fix a bug found while running couchbeam tests.
http_parser: always return `{done, binary()}` when the parsing is done.
fix doc typo
bump expm
s/manner/fashion
add Anthony Ramine copyright
add Magnus Klaar copyright
fix tohex (0-15)

spotted by @essen on IRC
add content_disposition/1 to parse a content disposition.
chk/start

	neue Datei:   test/NOTE.md
	neue Datei:   test/hackney_date_tests.erl
add the possibility to pass params to headers
calculate the content lenght of a multipart stream.

Some servers like NGINX don't handle a multipart stream sent with a
chunked encoding request. This change add the possibility to calculate
the full content length before sending the parts.

breaking changes:

- hackney_multipart:encode_form/1 has been rewritten to take new messages so we can return the content-length with the binary.
- mp_header/4 has been removed
document changes.
bump to 0.2.0
fix part eof

Initial part should not start withj \r\n. We are fixing it by appending
it to the end of part instead. Also make sure the len_mp_stream reflect
that change.
bump to 0.2.1
sync doc
don't quote params
fix hackney_url:unparse_url/1
don't url encode the value