enhance staging mode in order to show errors and web_console

Gemfile

@@ -42,7 +42,7 @@ gem 'd3-rails'
 gem 'rest-client'
 gem 'rubyzip'
 
-group :development do
+group :development, :staging do
   gem 'better_errors', platform: :ruby
   gem 'binding_of_caller', platform: :ruby
   gem 'capistrano', '~> 3.3.0'
@@ -56,7 +56,7 @@ group :development do
   gem 'web-console', '~> 2.0', platform: :ruby
 end
 
-group :development, :test do
+group :development, :test, :staging do
   gem 'byebug', platform: :ruby
   gem 'spring'
 end