Clamp results of NodeSet#first to length of NodeSet

[Derenge]

NodeSet#first did not perform the same as Enumberable#first

An example from ruby doc being:

%w[foo bar baz].first(10) #=> ["foo", "bar", "baz"]

What was expected:

Nokogiri::HTML('').css('a').first(3)
[#<Nokogiri::XML::Element:0x3fc3dfd5f1c8 name="a">, #<Nokogiri::XML::Element:0x3fc3dfd5f1b4 name="a">]

What was received:

Nokogiri::HTML('').css('a').first(3)
[#<Nokogiri::XML::Element:0x3fc3dfd5f1c8 name="a">, #<Nokogiri::XML::Element:0x3fc3dfd5f1b4 name="a">, nil]

[Derenge]

I'm unsure how to address the failing concourse build

[flavorjones]

@Derenge see #1654 for updates on debugging the failed build ... working on it.

[flavorjones]

@Derenge if you'd like to rebase off of 451d598 or later, the Concourse CI build will re-run and should pass. Sorry for the inconvenience.

[Derenge]

Is there anything I need to do to move this along?

[flavorjones]

Sorry for the delay, I've not spent much time on OSS lately. Merging now ...

[flavorjones]

Merged! Thank you so much for contributing, and for your patience. I've thanked you in the CHANGELOG.