Add development group to Gemfile

Gemfile

@@ -9,3 +9,12 @@ group :test do
   gem 'rubycritic', require: false
   gem 'slim_lint', require: false
 end
+
+group :development do
+  gem 'awesome_print', require: 'ap' # https://github.com/awesome-print/awesome_print
+  gem 'better_errors' # https://github.com/BetterErrors/better_errors
+  gem 'binding_of_caller' # better output of with variables for better_errors
+  gem 'bullet', require: !ENV['BULLET'].nil? # https://github.com/flyerhzm/bullet
+  gem 'pry-byebug'
+  gem 'pry-doc'
+end