Bump Ruby 2.4.2

Author: Thibaut

.ruby-version

@@ -1 +1 @@
-2.4.1
+2.4.2

Dockerfile

@@ -1,4 +1,4 @@
-FROM ruby:2.4.1
+FROM ruby:2.4.2
 
 WORKDIR /devdocs
 

Dockerfile-alpine

@@ -1,4 +1,4 @@
-FROM ruby:2.4.1-alpine
+FROM ruby:2.4.2-alpine
 
 WORKDIR /devdocs
 

Gemfile

@@ -1,5 +1,5 @@
 source 'https://rubygems.org'
-ruby '2.4.1'
+ruby '2.4.2'
 
 gem 'rake'
 gem 'thor'

Gemfile.lock

@@ -153,7 +153,7 @@ DEPENDENCIES
   yajl-ruby
 
 RUBY VERSION
-   ruby 2.4.1p111
+   ruby 2.4.2p198
 
 BUNDLED WITH
-   1.14.1
+   1.15.4

README.md

@@ -20,7 +20,7 @@ Unless you wish to contribute to the project, I recommend using the hosted versi
 
 DevDocs is made of two pieces: a Ruby scraper that generates the documentation and metadata, and a JavaScript app powered by a small Sinatra app.
 
-DevDocs requires Ruby 2.4.1, libcurl, and a JavaScript runtime supported by [ExecJS](https://github.com/rails/execjs#readme) (included in OS X and Windows; [Node.js](https://nodejs.org/en/) on Linux). Once you have these installed, run the following commands:
+DevDocs requires Ruby 2.4.2, libcurl, and a JavaScript runtime supported by [ExecJS](https://github.com/rails/execjs#readme) (included in OS X and Windows; [Node.js](https://nodejs.org/en/) on Linux). Once you have these installed, run the following commands:
 
 ```
 git clone https://github.com/Thibaut/devdocs.git && cd devdocs