move activesupport as a development dependency

Author: Jerry Cheung

html-pipeline.gemspec

@@ -21,7 +21,7 @@ Gem::Specification.new do |gem|
   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" ? [">= 2", "< 4"] : ">= 2"
 
+  gem.add_development_dependency "activesupport", RUBY_VERSION < "1.9.3" ? [">= 2", "< 4"] : ">= 2"
   gem.add_development_dependency "github-linguist", "~> 2.6.2"
 end