fix: Add Auth header to individual batch requests

* Fixes an issue where the authorization HTTP header wasn't
  being applied to individual batch requests.

[pr #822, refs #817]

lib/google/apis/core/batch.rb

@@ -177,6 +177,8 @@ module Google
           call.header.each do |key, value|
             request_head << sprintf("\r\n%s: %s", key, value)
           end
+          token = call.options.authorization
+          request_head << "\r\nAuthorization: Bearer #{token}" unless token.nil?
           request_head << sprintf("\r\nHost: %s", call.url.host)
           request_head << "\r\n\r\n"
           StringIO.new(request_head)

spec/google/apis/core/service_spec.rb

@@ -277,13 +277,14 @@ EOF
 --outer
 Content-Type: application/http
 Content-Id: <b1981e17-f622-49af-b2eb-203308b1b17d+0>
-Content-Length: 349
+Content-Length: 380
 Content-Transfer-Encoding: binary
 
 POST /upload/zoo/animals? HTTP/1.1
 X-Goog-Api-Client: #{x_goog_api_client_value}
 Content-Type: multipart/related; boundary=inner
 X-Goog-Upload-Protocol: multipart
+Authorization: Bearer a token
 Host: www.googleapis.com
 
 --inner