Update ruby-haml to 4.0.5.

# Haml Changelog

=======
## 4.0.5

Released on Jan 7, 2014 ([diff](https://github.com/haml/haml/compare/4.0.4...4.0.5)).

* Fix haml_concat appending unescaped HTML after a call to haml_tag.
* Fix for bug whereby when HAML :ugly option is "true",
  ActionView::Helpers::CaptureHelper::capture returns the whole view buffer
  when passed a block that returns nothing (thanks [Mircea
  Moise](https://github.com/mmircea16)).

## 4.0.4

Released on November 5, 2013 ([diff](https://github.com/haml/haml/compare/4.0.3...4.0.4)).

* Check for Rails::Railtie rather than Rails (thanks [Konstantin Shabanov](https://github.com/etehtsea)).
* Parser fix to allow literal '#' with suppress_eval (Matt Wildig).
* Helpers#escape_once works on frozen strings (as does
  ERB::Util.html_escape_once for which it acts as a replacement in
  Rails (thanks [Patrik Metzmacher](https://github.com/patrik)).
* Minor test fix (thanks [Mircea Moise](https://github.com/mmircea16)).

(taca)