Update default_value to fix: Protected methods do not respond on ruby 2.0.

https://github.com/FooBarWidget/default_value_for/commit/6f5a7ff4eea5ec446d43fe82deab47a7d77aada4
Available in these git tags: release-3.0.0.1 release-3.0.0 release-2.0.3 release-2.0.2

Came from this PR:
https://github.com/FooBarWidget/default_value_for/pull/29
Force ASCII-8BIT since the default encoding for scripts is UTF-8 in 2.0.

See https://www.ruby-lang.org/en/news/2013/02/24/ruby-2-0-0-p0-is-released/