Bump puma from 3.12.1 to 4.0.1

Bumps [puma](https://github.com/puma/puma) from 3.12.1 to 4.0.1.
- [Release notes](https://github.com/puma/puma/releases)
- [Changelog](https://github.com/puma/puma/blob/master/History.md)
- [Commits](https://github.com/puma/puma/compare/v3.12.1...v4.0.1)

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

Gemfile

@@ -32,7 +32,7 @@ gem "acts_as_list"
 gem "aasm", '~> 3.4.0'
 gem "htmlentities"
 gem "rails_autolink"
-gem 'puma', '~> 3.12'
+gem 'puma', '~> 4.0'
 gem 'paperclip'
 
 # To use ActiveModel has_secure_password

Gemfile.lock

@@ -147,7 +147,8 @@ GEM
     parallel (1.17.0)
     parser (2.6.3.0)
       ast (~> 2.4.0)
-    puma (3.12.1)
+    puma (4.0.1)
+      nio4r (~> 2.0)
     rack (2.0.7)
     rack-mini-profiler (1.0.2)
       rack (>= 1.2.0)
@@ -291,7 +292,7 @@ DEPENDENCIES
   mocha
   mysql2 (~> 0.5.2)
   paperclip
-  puma (~> 3.12)
+  puma (~> 4.0)
   rack-mini-profiler
   rails (~> 5.2.3)
   rails-controller-testing