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/

This is compatible with ruby 1.9.3 and 2.0+.

Fixes a travis failure on ruby 2.0:
```
  10) MiqLdap #sid_to_s
     Failure/Error: MiqLdap.sid_to_s(data).should == "S-1-5-21-4106323499-3255682937-2389761597-1183"
     ArgumentError:
       invalid byte sequence in UTF-8
     # /home/travis/.rvm/gems/ruby-2.0.0-p451/bundler/gems/rails-f9749c2ef83b/activesupport/lib/active_support/core_ext/object/blank.rb:105:in `=~'
     # /home/travis/.rvm/gems/ruby-2.0.0-p451/bundler/gems/rails-f9749c2ef83b/activesupport/lib/active_support/core_ext/object/blank.rb:105:in `!~'
     # /home/travis/.rvm/gems/ruby-2.0.0-p451/bundler/gems/rails-f9749c2ef83b/activesupport/lib/active_support/core_ext/object/blank.rb:105:in `blank?'
     # ./lib/miq_ldap.rb:445:in `sid_to_s'
     # ./spec/lib/miq_ldap_spec.rb:124:in `block (2 levels) in <top (required)>'
     # /home/travis/.rvm/gems/ruby-2.0.0-p451/gems/rspec-core-2.12.2/lib/rspec/core/example.rb:114:in `instance_eval'
     # /home/travis/.rvm/gems/ruby-2.0.0-p451/gems/rspec-core-2.12.2/lib/rspec/core/example.rb:114:in `block in run'
     # /home/travis/.rvm/gems/ruby-2.0.0-p451/gems/rspec-core-2.12.2/lib/rspec/core/example.rb:254:in `with_around_each_hooks'
     # /home/travis/.rvm/gems/ruby-2.0.0-p451/gems/rspec-core-2.12.2/lib/rspec/core/example.rb:111:in `run'
     # /home/travis/.rvm/gems/ruby-2.0.0-p451/gems/rspec-core-2.12.2/lib/rspec/core/example_group.rb:388:in `block in run_examples'
     # /home/travis/.rvm/gems/ruby-2.0.0-p451/gems/rspec-core-2.12.2/lib/rspec/core/example_group.rb:384:in `map'
     # /home/travis/.rvm/gems/ruby-2.0.0-p451/gems/rspec-core-2.12.2/lib/rspec/core/example_group.rb:384:in `run_examples'
     # /home/travis/.rvm/gems/ruby-2.0.0-p451/gems/rspec-core-2.12.2/lib/rspec/core/example_group.rb:369:in `run'
     # /home/travis/.rvm/gems/ruby-2.0.0-p451/gems/rspec-core-2.12.2/lib/rspec/core/command_line.rb:28:in `block (2 levels) in run'
     # /home/travis/.rvm/gems/ruby-2.0.0-p451/gems/rspec-core-2.12.2/lib/rspec/core/command_line.rb:28:in `map'
     # /home/travis/.rvm/gems/ruby-2.0.0-p451/gems/rspec-core-2.12.2/lib/rspec/core/command_line.rb:28:in `block in run'
     # /home/travis/.rvm/gems/ruby-2.0.0-p451/gems/rspec-core-2.12.2/lib/rspec/core/reporter.rb:34:in `report'
     # /home/travis/.rvm/gems/ruby-2.0.0-p451/gems/rspec-core-2.12.2/lib/rspec/core/command_line.rb:25:in `run'
     # /home/travis/.rvm/gems/ruby-2.0.0-p451/gems/rspec-core-2.12.2/lib/rspec/core/runner.rb:80:in `run'
     # /home/travis/.rvm/gems/ruby-2.0.0-p451/gems/rspec-core-2.12.2/lib/rspec/core/runner.rb:17:in `block in autorun'
```