Add 'set delimiter' functionality for {{{html_safe_tags}}}

[alfiehanssen]

We can already override {{normal_tags}} with our own custom delimiters, it would be VERY useful to be able to do the same for {{{html_safe_tags}}}, currently throws an error and returns a nil string.

[groue]

Hi Alfie.

http://mustache.github.com/mustache.5.html describes the "official" way to render unescaped values with custom delimiters:

You can also use & to unescape a variable: {{& name}}. This may be useful when changing delimiters (see "Set Delimiter" below).

Happy Mustache!