[Haml] Silence regexp match warnings.

Closes gh-103

doc-src/HAML_CHANGELOG.md

@@ -10,6 +10,8 @@
 
 * Don't remove `\n` in filters with interpolation.
 
+* Silence those annoying `"regexp match /.../n against to UTF-8 string"` warnings.
+
 ## 2.2.22
 
 [Tagged on GitHub](http://github.com/nex3/haml/commit/2.2.22).

lib/haml/helpers.rb

@@ -502,7 +502,7 @@ END
     # @param text [String] The string to sanitize
     # @return [String] The sanitized string
     def html_escape(text)
-      text.to_s.gsub(/[\"><&]/n) {|s| HTML_ESCAPE[s]}
+      Haml::Util.silence_warnings {text.to_s.gsub(/[\"><&]/n) {|s| HTML_ESCAPE[s]}}
     end
 
     # Escapes HTML entities in `text`, but without escaping an ampersand