Improved error messages in fill_buffer method.
Moved inline templates out of body of class but still in same file.

lldb isn't happy in either case.
Fixed bug on reading binary data.

See comment in http_streambuf::underflow(). Take home message is that
underflow and friends return and int.

traits_type<char> gives EOF as

int EOF = -1;

traits_type::int_type(0xff) != traits_type::to_int_type(0xff).

The latter is 255, the former is -1.
Small stuff.
Added Xcode project.