Simplify HTTP::Connection#read_headers!

[janko]

This simplifies the implementation of HTTP::Connection#read_headers!, the behaviour should be preserved.

[ixti]

I have a feeling that there was a reason why this part was written like that. read_more feeds data to the parser, so it should be performed before asking parser about anything.

[tarcieri]

Looks good, thanks!

[tarcieri]

Oh whoops, just noticed @ixti's comment now. My bad.

[janko]

@ixti From the functionality perspective it should be the same, as the @headers variable is defined only after all headers are received. If you'd find it more intuitive that @parser.headers? is called after the first read_more, I could swap

until @parser.headers?
  # ...
end

with

begin
 # ...
end until @parser.headers?

[ixti]

I think that's fine in fact. I might have mistook this with other place - and as we don't have specs for this it seems like more likely.

[ixti]

@janko-m I was referring a bit different thing. But let's keep what you have did. If we will face any issues - we will redo this :D