Add "uglifier" gem for es6 compression

Gemfile

@@ -13,6 +13,7 @@ gem 'SyslogLogger', '2.0', require: 'syslog/logger'
 gem 'iso8601',      '0.8.6' # for dates and times
 gem 'rails',        '4.2.10' # when update, all initializers eis_custom files needs check/update
 gem 'rest-client'
+gem 'uglifier'
 
 # load env
 gem 'figaro', '1.1.1'

Gemfile.lock

@@ -439,6 +439,8 @@ GEM
     tilt (1.4.1)
     tzinfo (1.2.5)
       thread_safe (~> 0.1)
+    uglifier (4.1.11)
+      execjs (>= 0.3.0, < 3)
     unf (0.1.4)
       unf_ext
     unf_ext (0.0.7.2)
@@ -536,6 +538,7 @@ DEPENDENCIES
   simpleidn (= 0.0.7)
   spring
   spring-commands-rspec
+  uglifier
   uuidtools (= 2.1.5)
   validates_email_format_of (= 1.6.3)
   webmock

config/environments/production.rb

@@ -23,7 +23,7 @@ Rails.application.configure do
   config.serve_static_files = false
 
   # Compress JavaScripts and CSS.
-  # config.assets.js_compressor = :uglifier
+  config.assets.js_compressor = Uglifier.new(harmony: true)
   # config.assets.css_compressor = :sass
 
   # Do not fallback to assets pipeline if a precompiled asset is missed.