Ruby 2.4.0 update

[Marius Bakke]

In good tradition, ruby made a new release today (25/12)[0].

I tried building some packages with the new version, but ruby-minitest
complains that Rake 12 is too new (even with the latest minitest). There
have been some core changes as well, with Fixnum and Bignum now merged
into a single Integer class.

I suggest that we keep ruby 2.3 as the main "ruby" variable until the
ecosystem catches up. Users will still get the latest version when
using `guix package` or `guix environment`. WDYT?

Patch attached. Not sure about the commit message.

0: https://www.ruby-lang.org/en/news/2016/12/25/ruby-2-4-0-released/

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>From 6f029cbaedf273febef92e9c4197c55414b818d5 Mon Sep 17 00:00:00 2001
From: Marius Bakke <address@hidden>
Date: Sun, 25 Dec 2016 18:07:47 +0100
Subject: [PATCH] gnu: ruby: Update to 2.4.0.

* gnu/packages/ruby.scm (ruby-2.4): New variable.
---
 gnu/packages/ruby.scm | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/gnu/packages/ruby.scm b/gnu/packages/ruby.scm
index c87f8b309..dee98c236 100644
--- a/gnu/packages/ruby.scm
+++ b/gnu/packages/ruby.scm
@@ -100,6 +100,20 @@ a focus on simplicity and productivity.")
     (home-page "https://ruby-lang.org";)
     (license license:ruby)))
 
+(define-public ruby-2.4
+  (package (inherit ruby)
+           (replacement #f)
+           (version "2.4.0")
+           (source
+            (origin
+              (method url-fetch)
+              (uri (string-append "https://cache.ruby-lang.org/pub/ruby/";
+                                  (version-major+minor version)
+                                  "/ruby-" version ".tar.xz"))
+              (sha256
+               (base32
+                "141nnsdk2q83c23p5kl404id8gy1ap261gin48rbjj5sbksgx1rs"))))))
+
 (define-public ruby-2.2
   (package (inherit ruby)
     (replacement #f)
-- 
2.11.0