Allow passing IO to HTML.build

[willhbr]

For example if you want to write directly to a TCPSocket or some other IO.

[willhbr]

Actually this doesn't really work, as HTML::Builder#build will always call .to_s on the IO so this is pointless.

I think the way to keep this flexible is to change the API a little:

• Keep HTML.build as the main string-returning entry point
• Make HTML::Builder.new always take an IO argument
• Create the String::Builder in HTML::Builder.build, like this:

def self.build : String
  String.build do |io|
    new(io).build do |builder|
      with builder yield builder
    end
  end
end

@ysbaddaden does that sound reasonable? Otherwise I'll just patch this in my project to get it working how I need

[ysbaddaden]

That sounds reasonable, the buffer shall be a general IO and be created by the .build constructor, not by #initialize.

We can keep backward compatibility by deprecating the #initialize (no args) and #build methods, and adding:

• .build(IO) overload
• #initialize(io : IO)
• protected #build_impl (that don't call #to_s)

[willhbr]

Updated, let me know if that's not what you were thinking

[ysbaddaden]

Polish:

Suggested change

	String.build do |io|
	new(io).build_impl do |builder|
	with builder yield builder
	end
	end
	String.build { |io| build(io) }

[ysbaddaden]

Polish: no need to call #build_impl

Suggested change

	build_impl do
	with self yield self
	end
	with self yield self