fix#497
This changes the function signature to accept the `value_type`
instead of the entire message.
Actions Required:
* For any user-defined models of Body, change the function signature
to accept `value_type const&` and modify the function definition
accordingly.
* detail::read_size_helper is removed
* public function read_size helps determine the optimum
size for calls to a DynamicBuffer's prepare function.
* special case for Asio types which don't conform to
the concept but have their own helper function.
fix#446
* The ping_callback option struct is removed.
Actions Required:
* Change call sites which use ping_callback with set_option to
call stream::ping_callback instead.
fix#446
* The write_buffer_size option struct is removed.
Actions Required:
* Change call sites which use write_buffer_size with set_option to
call stream::write_buffer_size instead.
fix#446
* The read_message_max option struct is removed.
Actions Required:
* Change call sites which use read_message_max with set_option to
call stream::read_message_max instead.
fix#446
* The read_buffer_size option struct is removed
Actions Required:
* Change call sites which use read_buffer_size with set_option to
call stream::read_buffer_size instead.
fix#446
* message_type is removed
Actions Required:
* Change call sites which use message_type with set_option
to call stream::binary or stream::text instead.
fix#374, fix#446
* auto_fragment option struct is removed
Actions Required:
* Change call sites which use auto_fragment with set_option
to call stream::auto_fragment instead.
Vinnie Falco