FYI: a new "absent operator" on Ruby 2.4.1

[hachi8833]

This is NOT an issue and just to let you know that a new "absent operator" has been implemented on Ruby's regexp lib named Onigmo. Sorry for this if this'd disturb you.

• https://medium.com/rubyinside/the-new-absent-operator-in-ruby-s-regular-expressions-7c3ef6cd0b99#.mmo5txduy

Note that the implementation of the operator has a rigid background theory: https://staff.aist.go.jp/tanaka-akira/pub/prosym49-akr-paper.pdf

I recognize that your Regexp2 is based upon .NET Framework and extending your lib like that might not be good in some cases. Note that I don't mean I need the operator right now. I just wrote that for the case you'd have any interests in the new operator.

Cheers,