Upgrade ruby Sass and dependencies

Gemfile

@@ -1,2 +1,2 @@
 source 'https://rubygems.org'
-gem 'sass', '~> 3.5.5'
+gem 'sass', '~> 3.5.6'

Gemfile.lock

@@ -1,11 +1,11 @@
 GEM
   remote: https://rubygems.org/
   specs:
-    ffi (1.9.18)
-    rb-fsevent (0.10.2)
+    ffi (1.9.25)
+    rb-fsevent (0.10.3)
     rb-inotify (0.9.10)
       ffi (>= 0.5.0, < 2)
-    sass (3.5.5)
+    sass (3.5.7)
       sass-listen (~> 4.0.0)
     sass-listen (4.0.0)
       rb-fsevent (~> 0.9, >= 0.9.4)
@@ -15,7 +15,7 @@ PLATFORMS
   ruby
 
 DEPENDENCIES
-  sass (~> 3.5.5)
+  sass (~> 3.5.6)
 
 BUNDLED WITH
-   1.16.1
+   1.16.6