Bump thin from 1.7.2 to 1.8.0

Bumps [thin](https://github.com/macournoyer/thin) from 1.7.2 to 1.8.0.
- [Release notes](https://github.com/macournoyer/thin/releases)
- [Changelog](https://github.com/macournoyer/thin/blob/master/CHANGELOG)
- [Commits](https://github.com/macournoyer/thin/commits)

Signed-off-by: dependabot[bot] <support@github.com>

Gemfile

@@ -31,7 +31,7 @@ gem 'sdoc', '~> 2.0', group: :doc
 gem 'foreman', '~> 0.87'
 
 group :production do
-  gem 'thin', '~> 1.7'
+  gem 'thin', '~> 1.8'
   gem 'rails_12factor', '~> 0.0'
   gem 'puma', '~> 5.0'
 end

Gemfile.lock

@@ -733,7 +733,7 @@ GEM
     therubyracer (0.12.3)
       libv8 (~> 3.16.14.15)
       ref
-    thin (1.7.2)
+    thin (1.8.0)
       daemons (~> 1.0, >= 1.0.9)
       eventmachine (~> 1.0, >= 1.0.4)
       rack (>= 1, < 3)
@@ -840,7 +840,7 @@ DEPENDENCIES
   spring (~> 2.1)
   sqlite3 (~> 1.4)
   therubyracer (~> 0.12)
-  thin (~> 1.7)
+  thin (~> 1.8)
   timecop (~> 0.9)
   travis (~> 1.8)
   turbolinks (~> 5.2)