remove ignore for gemfile and gemfile.lock, re-add mysql2

.gitignore

@@ -43,5 +43,5 @@ config/deploy/config/*
 .byebug_history
 
 # Gem files
-Gemfile
-Gemfile.lock
+#Gemfile
+#Gemfile.lock

Gemfile

@@ -9,7 +9,7 @@ end
 # Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
 gem 'rails', '~> 5.1.0'
 # Use mysql as the database for Active Record
-#gem 'mysql2', '>= 0.3.18', '< 0.5'
+gem 'mysql2', '>= 0.3.18', '< 0.5'
 
 #Use PosgreSQL
 gem 'pg'

Gemfile.lock

@@ -114,6 +114,7 @@ GEM
     mini_portile2 (2.1.0)
     minitest (5.10.2)
     multi_json (1.12.1)
+    mysql2 (0.4.6)
     nio4r (2.1.0)
     nokogiri (1.7.2)
       mini_portile2 (~> 2.1.0)
@@ -251,6 +252,7 @@ DEPENDENCIES
   jquery-rails
   kaminari!
   listen (~> 3.0.5)
+  mysql2 (>= 0.3.18, < 0.5)
   pg
   prawn
   prawn-table