Add maybe_const_t
Add shared_iterator
Allow reference types in is_call_possible
Improve asio::buffer_sequence
Allow empty shared_handler
Add HTTP protocol and client support:
* http::client_session for making requests
* http::raw_parser for parsing message objects
* Move joyent parser code into namespace joyent
* Rename includes for joyent parser unity wrapper
* error_code and detail support functions for joyent parser
* Add a large URL data set for unit tests