Bump puma from 3.12.2 to 3.12.3 (#9)

Bumps [puma](https://github.com/puma/puma) from 3.12.2 to 3.12.3.
- [Release notes](https://github.com/puma/puma/releases)
- [Changelog](https://github.com/puma/puma/blob/master/History.md)
- [Commits](puma/puma@v3.12.2...v3.12.3)

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

Author: dependabot[bot]

Gemfile

@@ -12,7 +12,7 @@ gem 'rails', '~> 5.1.6'
 # Use sqlite3 as the database for Active Record
 gem 'sqlite3', '~> 1.3.7'
 # Use Puma as the app server
-gem 'puma', '~> 3.7'
+gem 'puma', '~> 3.12'
 # Use SCSS for stylesheets
 gem 'sass-rails', '~> 5.0'
 # Use Uglifier as compressor for JavaScript assets

Gemfile.lock

@@ -116,7 +116,7 @@ GEM
       mini_portile2 (~> 2.4.0)
     popper_js (1.16.0)
     public_suffix (4.0.3)
-    puma (3.12.2)
+    puma (3.12.3)
     rack (2.2.2)
     rack-test (1.1.0)
       rack (>= 1.0, < 3)
@@ -226,7 +226,7 @@ DEPENDENCIES
   jbuilder (~> 2.5)
   jquery-rails
   listen
-  puma (~> 3.7)
+  puma (~> 3.12)
   rails (~> 5.1.6)
   rest-client
   sass-rails (~> 5.0)