Update React on Rails to v12 (#470)

* fix travis, update ruby version
* update ruby version

Author: hussainakram

.rubocop.yml

@@ -3,7 +3,7 @@
 
 AllCops:
   DisplayCopNames: true
-  TargetRubyVersion: 2.2
+  TargetRubyVersion: 2.7
   Include:
     - '**/Rakefile'
     - '**/config.ru'

.travis.yml

@@ -1,10 +1,11 @@
 language: ruby
 
 rvm:
-  - 2.5.3
+  - 2.7.1
 
 services:
   - docker
+  - postgresql
 
 notifications:
   slack: shakacode:YvfXbuFMcFAHt6ZjABIs0KET

Gemfile

@@ -1,7 +1,9 @@
+# frozen_string_literal: true
+
 source "https://rubygems.org"
-ruby "2.5.3"
+ruby "2.7.1"
 
-gem "react_on_rails", "11.2.2"
+gem "react_on_rails", "12.0.0-beta.1"
 gem "webpacker"
 
 # Bundle edge Rails instead: gem "rails", github: "rails/rails"