Bump puma from 3.12.0 to 4.3.8

Gemfile

@@ -8,7 +8,7 @@ gem 'rails', '~> 5.2.2.1'
 # 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', '~> 4.3'
 # Build JSON APIs with ease. Read more: https://github.com/rails/jbuilder
 gem 'jbuilder', '~> 2.5'
 # Use Redis adapter to run Action Cable in production

Gemfile.lock

@@ -190,7 +190,9 @@ GEM
     mime-types (3.2.2)
       mime-types-data (~> 3.2015)
     mime-types-data (3.2018.0812)
-    mimemagic (0.3.3)
+    mimemagic (0.3.10)
+      nokogiri (~> 1)
+      rake
     mini_mime (1.0.1)
     mini_portile2 (2.4.0)
     minitest (5.11.3)
@@ -217,7 +219,8 @@ GEM
       pry (>= 0.10.4)
     psych (3.1.0)
     public_suffix (3.0.3)
-    puma (3.12.0)
+    puma (4.3.8)
+      nio4r (~> 2.0)
     raabro (1.1.6)
     rack (2.0.6)
     rack-cors (1.0.2)
@@ -424,7 +427,7 @@ DEPENDENCIES
   pg (>= 0.18, < 2.0)
   pry-byebug
   pry-rails
-  puma (~> 3.11)
+  puma (~> 4.3)
   rack-cors
   rails (~> 5.2.2.1)
   rails_admin (~> 1.4)