New classes are introduced to represent HTTP messages and their
associated bodies. The parser interface is reworked to use CRTP,
error codes, and trait checks.
New classes:
* basic_headers
Models field/value pairs in a HTTP message.
* message
Models a HTTP message, body behavior defined by template argument.
Parsed message carries metadata generated during parsing.
* parser
Produces parsed messages.
* empty_body, string_body, basic_streambuf_body
Classes used to represent content bodies in various ways.
New functions:
* read, async_read, write, async_write
Read and write HTTP messages on a socket.
New concepts:
* Body: Represents the HTTP Content-Body.
* Field: A HTTP header field.
* FieldSequence: A forward sequence of fields.
* Reader: Parses a Body from a stream of bytes.
* Writer: Serializes a Body to buffers.
basic_parser changes:
* add write methods which throw exceptions instead
* error_code passed via parameter instead of return value
* fold private member calls into existing callbacks
* basic_parser uses CRTP instead of virtual members
* add documentation on Derived requirements for CRTP
impl/http-parser changes:
* joyent renamed to nodejs to reflect upstream changes
