def use(ruby_string, opts = {})
      ruby_string = ruby_string.to_s
      result = rvm(:use, ruby_string)
      successful = result.successful?
      if successful
        @environment_name = ruby_string
        @expanded_name    = nil
        use_env_from_result! result if opts[:replace_env]
      end
      successful
    end
def use(ruby_string, opts = {})
      ruby_string = ruby_string.to_s
      result = rvm(:use, ruby_string)
      successful = result.successful?
      if successful
        @environment_name = ruby_string
        @expanded_name    = nil
        use_env_from_result! result if opts[:replace_env]
      end
      successful
    end
Changes the ruby string for the current environment.

 env.use '1.9.2' # => true
 env.use 'ree' # => true
 env.use 'foo' # => false