Merged r14167 from trunk to 3.0-stable

Gemfile: pin rmagick version 2.13

rmagick 2.14 prints
'[DEPRECATION] requiring "RMagick" is deprecated. Use "rmagick" instead'.

git-svn-id: http://svn.redmine.org/redmine/branches/3.0-stable@14168 e93f8b46-1217-0410-a6f0-8f06a7374b81

Gemfile

@@ -32,7 +32,7 @@ end
 platforms :mri, :mingw, :x64_mingw do
   # Optional gem for exporting the gantt to a PNG file, not supported with jruby
   group :rmagick do
-    gem "rmagick", ">= 2.0.0"
+    gem "rmagick", "~> 2.13.4"
   end
 
   # Optional Markdown support, not for JRuby