add lower bounds to dependencies

Author: Jerry Cheung

html-pipeline.gemspec

@@ -16,12 +16,12 @@ Gem::Specification.new do |gem|
   gem.require_paths = ["lib"]
 
   gem.add_dependency "gemoji",          "~> 1.0"
-  gem.add_dependency "nokogiri",        RUBY_VERSION < "1.9.2" ? "< 1.6" : "~> 1.4"
+  gem.add_dependency "nokogiri",        RUBY_VERSION < "1.9.2" ? [">= 1.4", "< 1.6"] : "~> 1.4"
   gem.add_dependency "github-markdown", "~> 0.5"
-  gem.add_dependency "sanitize",        RUBY_VERSION < "1.9.2" ? "< 2.0.4" : "~> 2.0"
+  gem.add_dependency "sanitize",        RUBY_VERSION < "1.9.2" ? [">= 2", "< 2.0.4"] : "~> 2.0"
   gem.add_dependency "rinku",           "~> 1.7"
   gem.add_dependency "escape_utils",    "~> 0.3"
-  gem.add_dependency "activesupport",   RUBY_VERSION < "1.9.3" ? "< 4" : ">= 2"
+  gem.add_dependency "activesupport",   RUBY_VERSION < "1.9.3" ? [">= 2", "< 4"] : ">= 2"
 
   gem.add_development_dependency "github-linguist", "~> 2.6.2"
 end