Merge branch 'bump-gitlab-git' into 'master'

Bump gitlab git

Makes Commit#find method much faster on bigger repos.

Partly fixes #1306

Gemfile.lock

@@ -175,7 +175,7 @@ GEM
       mime-types (~> 1.19)
     gitlab_emoji (0.0.1.1)
       emoji (~> 1.0.1)
-    gitlab_git (5.8.0)
+    gitlab_git (5.9.0)
       activesupport (~> 4.0)
       charlock_holmes (~> 0.6)
       gitlab-grit (~> 2.6)
@@ -534,7 +534,7 @@ GEM
       eventmachine (>= 0.12.8)
       http_parser.rb (~> 0.5.1)
       simple_oauth (~> 0.1.4)
-    tzinfo (1.2.0)
+    tzinfo (1.2.1)
       thread_safe (~> 0.1)
     uglifier (2.3.2)
       execjs (>= 0.3.0)