bump puma version

Gemfile

@@ -6,26 +6,24 @@ git_source(:github) do |repo_name|
   "https://github.com/#{repo_name}.git"
 end
 
-gem 'rails',                   '~> 5.0.1'
-gem 'pg',                      '~> 0.19.0'
-gem 'puma',                    '~> 3.0'
-gem 'sass-rails',              '~> 5.0'
-gem 'coffee-rails',            '~> 4.2.1'
-gem 'jquery-rails',            '~> 4.2.2'
-gem 'uglifier',                '>= 1.3.0'
-gem 'turbolinks',              '~> 5'
-gem 'jbuilder',                '~> 2.5'
-gem 'httparty',                '~> 0.16.2'
-gem 'figaro',                   git: 'https://github.com/zaimramlan/figaro.git'
+gem 'rails', '~> 5.0.1'
+gem 'pg', '~> 0.19.0'
+gem 'puma', '~> 3.12.1'
+gem 'sass-rails', '~> 5.0'
+gem 'coffee-rails', '~> 4.2.1'
+gem 'jquery-rails', '~> 4.2.2'
+gem 'uglifier', '>= 1.3.0'
+gem 'turbolinks', '~> 5'
+gem 'jbuilder', '~> 2.5'
+gem 'httparty', '~> 0.16.2'
+gem 'figaro', git: 'https://github.com/zaimramlan/figaro.git'
 gem 'nokogiri'
 
 group :development do
-  gem 'web-console',           '>= 3.3.0'
-  gem 'spring',                '~> 2.0'
+  gem 'web-console', '>= 3.3.0'
+  gem 'spring', '~> 2.0'
   gem 'spring-watcher-listen', '~> 2.0.0'
-  gem 'byebug',                '~> 9.0', '>= 9.0.6',  platform: :mri
-  gem 'listen',                '~> 3.0.5'  
-  gem 'awesome_print',         '~> 1.7'
+  gem 'byebug', '~> 9.0', '>= 9.0.6',  platform: :mri
+  gem 'listen', '~> 3.0.5'
+  gem 'awesome_print', '~> 1.7'
 end
-
-gem 'tzinfo-data', platforms: [:mingw, :mswin, :x64_mingw, :jruby]

Gemfile.lock

@@ -92,7 +92,7 @@ GEM
     nokogiri (1.7.0.1)
       mini_portile2 (~> 2.1.0)
     pg (0.19.0)
-    puma (3.6.2)
+    puma (3.12.1)
     rack (2.0.1)
     rack-test (0.6.3)
       rack (>= 1.0)
@@ -175,13 +175,12 @@ DEPENDENCIES
   listen (~> 3.0.5)
   nokogiri
   pg (~> 0.19.0)
-  puma (~> 3.0)
+  puma (~> 3.12.1)
   rails (~> 5.0.1)
   sass-rails (~> 5.0)
   spring (~> 2.0)
   spring-watcher-listen (~> 2.0.0)
   turbolinks (~> 5)
-  tzinfo-data
   uglifier (>= 1.3.0)
   web-console (>= 3.3.0)