Upgrade Ruby to 2.5.1

docker-library/ruby#196

Author: ledermann

.rubocop.yml

@@ -1,5 +1,5 @@
 AllCops:
-  TargetRubyVersion: 2.4
+  TargetRubyVersion: 2.5
   Exclude:
     - db/schema.rb
     - 'node_modules/**/*'

Dockerfile

@@ -1,6 +1,6 @@
 ######################
 # Stage: Builder
-FROM ruby:2.4.4-alpine3.7 as Builder
+FROM ruby:2.5.1-alpine as Builder
 
 ARG FOLDERS_TO_REMOVE
 ARG BUNDLE_WITHOUT
@@ -52,7 +52,7 @@ FROM madnight/docker-alpine-wkhtmltopdf as wkhtmltopdf
 
 ###############################
 # Stage Final
-FROM ruby:2.4.4-alpine3.7
+FROM ruby:2.5.1-alpine
 LABEL maintainer="mail@georg-ledermann.de"
 
 ARG ADDITIONAL_PACKAGES