Fix wrong order of issues when importing from github

See API details at https://developer.github.com/v3/issues/.
Refs #1791

CHANGELOG

 Please view this file on the master branch, on stable branches it's out of date.
 
 v 7.13.0 (unreleased)
+  - Fix order of issues imported form GitHub (Hiroyuki Sato)
   - Fix Merge Request webhook to properly fire "merge" action when accepted from the web UI
   - Add `two_factor_enabled` field to admin user API (Stan Hu)
   - Fix invalid timestamps in RSS feeds (Rowan Wookey)

lib/gitlab/github_import/importer.rb

@@ -11,7 +11,9 @@ module Gitlab
 
       def execute
         #Issues && Comments
-        client.list_issues(project.import_source, state: :all).each do |issue|
+        client.list_issues(project.import_source, state: :all,
+                                                  sort: :created,
+                                                  direction: :asc).each do |issue|
           if issue.pull_request.nil?
 
             body = @formatter.author_line(issue.user.login, issue.body)