Bump puma from 3.12.1 to 3.12.4

Bumps [puma](https://github.com/puma/puma) from 3.12.1 to 3.12.4.
- [Release notes](https://github.com/puma/puma/releases)
- [Changelog](https://github.com/puma/puma/blob/master/History.md)
- [Commits](puma/puma@v3.12.1...v3.12.4)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

Gemfile

@@ -8,7 +8,7 @@ gem 'rails', '~> 5.2.3'
 # Use postgresql as the database for Active Record
 gem 'pg', '>= 0.18', '< 2.0'
 # Use Puma as the app server
-gem 'puma', '~> 3.11'
+gem 'puma', '~> 3.12'
 # Use SCSS for stylesheets
 gem 'sass-rails', '~> 5.0'
 # Use Uglifier as compressor for JavaScript assets

Gemfile.lock

@@ -128,7 +128,7 @@ GEM
       method_source (~> 0.9.0)
     pry-rails (0.3.9)
       pry (>= 0.10.4)
-    puma (3.12.1)
+    puma (3.12.4)
     pusher-client (0.6.2)
       json
       websocket (~> 1.0)
@@ -260,7 +260,7 @@ DEPENDENCIES
   orderly
   pg (>= 0.18, < 2.0)
   pry-rails
-  puma (~> 3.11)
+  puma (~> 3.12)
   rack-cors
   rails (~> 5.2.3)
   redis (~> 4.0)