Content-Length fixes in Rack hello world example.
Content-Length fixes in Rack hello world example.

nning/david,EmuxEvans/david,Miradorn/david,EmuxEvans/david,EmuxEvans/david,Miradorn/david,Miradorn/david,nning/david,nning/david,Miradorn/david,Miradorn/david,nning/david,nning/david,EmuxEvans/david,EmuxEvans/david