Update kramdown version requirement

Kramdown has had a new release which includes some bugfixes mdl needed, so we
can use the release version now.

Author: mivok

Gemfile

@@ -1,4 +1,2 @@
 source 'https://rubygems.org'
 gemspec
-
-gem 'kramdown', '1.3.3', :git => 'https://github.com/gettalong/kramdown'

mdl.gemspec

@@ -20,7 +20,7 @@ Gem::Specification.new do |spec|
 
   spec.required_ruby_version = '>= 1.9.2'
 
-  spec.add_dependency "kramdown", "~> 1.3.0"
+  spec.add_dependency "kramdown", "~> 1.4.0"
 
   spec.add_development_dependency "bundler", "~> 1.5"
   spec.add_development_dependency "rake"