Bundle update

Gemfile.lock

 GIT
   remote: git://github.com/activeadmin/activeadmin.git
-  revision: 7ff122d580835d70cfc424bc251e70ab0ec51b3d
+  revision: 8ddc07eefb9c4c39f96e1ad990fe7789555fd4ff
   specs:
     activeadmin (1.0.0.pre4)
       arbre (~> 1.0, >= 1.0.2)
@@ -177,7 +177,7 @@ GEM
       haml (>= 4.0.6, < 5.0)
       html2haml (>= 1.0.1)
       railties (>= 4.0.1)
-    haml_lint (0.20.0)
+    haml_lint (0.21.0)
       haml (~> 4.0)
       rake (>= 10, < 13)
       rubocop (>= 0.47.0)