Fix a issue to use a CLI with the xargs.

# :ok_hand::ok_hand::ok_hand::ok_hand: Expected: :ok_hand::ok_hand::ok_hand::ok_hand:

```bash
$ echo http://example.com/ http://nokogiri.org | xargs -tn1 nokogiri -e 'p $_.css("title").text'
nokogiri -e p $_.css("title").text http://example.com/
"Example Domain"
nokogiri -e p $_.css("title").text http://nokogiri.org
"Nokogiri"
```

:smile: :notes:

# :hankey::hankey::hankey::hankey: Actual: :hankey::hankey::hankey::hankey:

```bash
$ nokogiri --version | head -1
# Nokogiri (1.6.1)

$ echo http://example.com/ http://nokogiri.org | xargs -tn1 nokogiri -e 'p $_.css("title").text'
nokogiri -e p $_.css("title").text http://example.com/
""
nokogiri -e p $_.css("title").text http://nokogiri.org
""
```

:fearful: :broken_heart: