Add cookie jar for handling HTTP redirection.

Add new cookie_jar method to responses, and reimplement cookies using
it. Also dup args when generating redirect options rather than mutating
the args on the response object.

lib/restclient/abstract_response.rb

@@ -1,4 +1,5 @@
 require 'cgi'
+require 'http-cookie'
 
 module RestClient
 
@@ -24,9 +25,28 @@ def raw_headers
 
     # Hash of cookies extracted from response headers
     def cookies
-      @cookies ||= (self.headers[:set_cookie] || {}).inject({}) do |out, cookie_content|
-        out.merge parse_cookie(cookie_content)
+      hash = {}
+
+      cookie_jar.cookies.each do |out, cookie|
+        hash[cookie.name] = cookie.value
       end
+
+      hash
+    end
+
+    # Cookie jar extracted from response headers.
+    #
+    # @return [HTTP::CookieJar]
+    #
+    def cookie_jar
+      return @cookie_jar if @cookie_jar
+
+      jar = HTTP::CookieJar.new
+      headers.fetch(:set_cookie, []).each do |cookie|
+        jar.parse(cookie, @args.fetch(:url))
+      end
+
+      @cookie_jar = jar
     end
 
     # Return the default behavior corresponding to the response code:
@@ -61,25 +81,28 @@ def description
 
     # Follow a redirection
     def follow_redirection request = nil, result = nil, & block
+      new_args = @args.dup
+
       url = headers[:location]
       if url !~ /^http/
         url = URI.parse(args[:url]).merge(url).to_s
       end
-      args[:url] = url
+      new_args[:url] = url
       if request
         if request.max_redirects == 0
           raise MaxRedirectsReached
         end
-        args[:password] = request.password
-        args[:user] = request.user
-        args[:headers] = request.headers
-        args[:max_redirects] = request.max_redirects - 1
-        # pass any cookie set in the result
-        if result && result['set-cookie']
-          args[:headers][:cookies] = (args[:headers][:cookies] || {}).merge(parse_cookie(result['set-cookie']))
-        end
+        new_args[:password] = request.password
+        new_args[:user] = request.user
+        new_args[:headers] = request.headers
+        new_args[:max_redirects] = request.max_redirects - 1
+
+        # TODO: figure out what to do with original :cookie, :cookies values
+        new_args[:headers]['Cookie'] = HTTP::Cookie.cookie_value(
+          cookie_jar.cookies(new_args.fetch(:url)))
       end
-      Request.execute args, &block
+
+      Request.execute(new_args, &block)
     end
 
     def self.beautify_headers(headers)