Bump Rugged to 0.27.0

Release notes: https://github.com/libgit2/libgit2/releases/tag/v0.27.0

This version solves a significant performance issue with generating
large diffs: https://github.com/libgit2/libgit2/issues/4460

Gemfile

@@ -28,7 +28,7 @@ gem 'default_value_for', gem_versions['default_value_for']
 gem 'mysql2', '~> 0.4.10', group: :mysql
 gem 'pg', '~> 0.18.2', group: :postgres
 
-gem 'rugged', '~> 0.26.0'
+gem 'rugged', '~> 0.27'
 gem 'grape-route-helpers', '~> 2.1.0'
 
 gem 'faraday', '~> 0.12'

Gemfile.lock

@@ -813,7 +813,7 @@ GEM
     rubyzip (1.2.1)
     rufus-scheduler (3.4.0)
       et-orbi (~> 1.0)
-    rugged (0.26.0)
+    rugged (0.27.0)
     safe_yaml (1.0.4)
     sanitize (2.1.0)
       nokogiri (>= 1.4.4)
@@ -1173,7 +1173,7 @@ DEPENDENCIES
   ruby-prof (~> 0.17.0)
   ruby_parser (~> 3.8)
   rufus-scheduler (~> 3.4)
-  rugged (~> 0.26.0)
+  rugged (~> 0.27)
   sanitize (~> 2.0)
   sass-rails (~> 5.0.6)
   scss_lint (~> 0.56.0)