instead is a shared_ptr

Conflicts:
	src/http.cc

Added a Date and a Raw header. Raw headers will be used when the parser encounters a header that it does not know. Raw headers only store strings for now

The reason is to avoid some headers name like Server or Date to collide
with some other generic classes that might have the same name

Also used the macro when checking if the subtype belongs to the vendor
tree.

Added an ArrayBuf class that provides an array-based streambuf so that response content can now be directly serialized to a fixed-size char buffer with standard iostream interface

The server now returns an HTTP Bad Request when parsing fails and returns a 500 when an exception is thrown

The parser is now associated to a particular connection (peer) so that it can parse a request from multiple tcp packets

Also started working on type-safe http headers parsing