Log Message:
Update erubis to version 2.5.0.  Changes from version 2.3.1 include:

+ Install as a Ruby gem.

- Ruby on Rails 2.0 support.

- Add new command-line property '--docwrite={true|false}' to
  Erubis::Ejavascript.  If this property is true then
  'document.write(_buf.join(""));' is used as postamble and if it is
  false then '_buf.join("")' is used.

- When using Erubis::Eruby#evaluate(), changing local variables in
  templates have affected to variables accessible with TOPLEVEL_BINDING.
  It means that if you change variables in templates, it is possible
  to change variables in main program.  This was a bug and is now
  fixed not to affect to variables in main program.

- Preprocessing is supported by Ruby on Rails helper.

- Erubis::Eruby#evaluate() (or Erubis::RubyEvaluator#evaluate()) now
  creates Proc object from @src and eval it.

- Erubis::Eruby#def_method() is supported.  This method defines ruby
  code as instance method or singleton metod.

- Erubis::XmlHelper.url_escape() and u() which is alias of url_escape()
  are added.