Fix remaining rubocop offences

Author: 5t111111

app/controllers/sessions_controller.rb

@@ -17,7 +17,7 @@ def create
 
     # Use cookies for ActionCable authorization
     cookies.signed[:user_id] = session[:user_id] = user.id
-    redirect_to root_url, notice: 'Logged in with Slack'
+    redirect_to root_url, notice: "Logged in with Slack"
   end
 
   def destroy

db/migrate/20160827120217_create_versions.rb

@@ -5,8 +5,8 @@ class CreateVersions < ActiveRecord::Migration
   # - `MysqlAdapter` - Used by gems: `mysql`, `activerecord-jdbcmysql-adapter`.
   # - `Mysql2Adapter` - Used by `mysql2` gem.
   MYSQL_ADAPTERS = [
-    'ActiveRecord::ConnectionAdapters::MysqlAdapter',
-    'ActiveRecord::ConnectionAdapters::Mysql2Adapter'
+    "ActiveRecord::ConnectionAdapters::MysqlAdapter",
+    "ActiveRecord::ConnectionAdapters::Mysql2Adapter"
   ].freeze
 
   # The largest text column available in all supported RDBMS is
@@ -72,7 +72,7 @@ def mysql?
     #
     def versions_table_options
       if mysql?
-        { options: 'ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_general_ci' }
+        { options: "ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_general_ci" }
       else
         {}
       end