update gitlab-grack to 2.0.0.rc2

Gemfile

@@ -41,7 +41,7 @@ gem "browser"
 gem "gitlab_git", '7.0.0.rc14'
 
 # Ruby/Rack Git Smart-HTTP Server Handler
-gem 'gitlab-grack', '~> 2.0.0.pre', require: 'grack'
+gem 'gitlab-grack', '~> 2.0.0.rc2', require: 'grack'
 
 # LDAP Auth
 gem 'gitlab_omniauth-ldap', '1.2.0', require: "omniauth-ldap"

Gemfile.lock

@@ -183,7 +183,7 @@ GEM
     gitlab-flowdock-git-hook (0.4.2.2)
       gitlab-grit (>= 2.4.1)
       multi_json
-    gitlab-grack (2.0.0.pre)
+    gitlab-grack (2.0.0.rc2)
       rack (~> 1.5.1)
     gitlab-grit (2.7.2)
       charlock_holmes (~> 0.6)
@@ -668,7 +668,7 @@ DEPENDENCIES
   gemnasium-gitlab-service (~> 0.2)
   github-markup
   gitlab-flowdock-git-hook (~> 0.4.2)
-  gitlab-grack (~> 2.0.0.pre)
+  gitlab-grack (~> 2.0.0.rc2)
   gitlab-linguist (~> 3.0.0)
   gitlab_emoji (~> 0.0.1.1)
   gitlab_git (= 7.0.0.rc14)