url
  http://example.com/index.html
expected
  abcdefghijklmnopqrstuvwxyz1234567890abcdef
headers
  Accept: */*
  X-Custom: This is a custom header
  x-lower: This is a lower-case custom header
  authorization: fake auth data
----------
GET /index.html HTTP/1.1
Host: example.com
Accept: */*
Authorization: fake auth data
Connection: close
User-Agent: HTTP-Tiny/VERSION
X-Custom: This is a custom header
x-lower: This is a lower-case custom header

----------
HTTP/1.1 200 OK
Date: Thu, 03 Feb 1994 00:00:00 GMT
Content-Type: text/plain
Content-Length: 44

abcdefghijklmnopqrstuvwxyz1234567890abcdef