Use Nokogiri 1.7.2 if possible (#26183).

Patch by Go MAEDA.

git-svn-id: https://svn.redmine.org/redmine/trunk@16676 e93f8b46-1217-0410-a6f0-8f06a7374b81

Gemfile

@@ -16,7 +16,7 @@ gem "roadie-rails", "~> 1.1.1"
 gem "roadie", "~> 3.2.1"
 gem "mimemagic"
 
-gem "nokogiri", (RUBY_VERSION >= "2.1" ? ">= 1.7.0" : "~> 1.6.8")
+gem "nokogiri", (RUBY_VERSION >= "2.1" ? "~> 1.7.2" : "~> 1.6.8")
 gem "i18n", "~> 0.7.0"
 gem "ffi", "1.9.14", :platforms => :mingw if RUBY_VERSION < "2.0"