Add Nokogiri::XML::Document#collect_namespaces_[href_keys|prefix_keys]

[wolfgangw]

See #885 for details

[wolfgangw]

Is someone willing to help set me up for how to add the required tests for this? I'd like to get it off our desks, either way. Thanks in advance.

[wolfgangw]

Lee, I used inject to align with collect_namespaces which uses the same method. Maybe change this in all 3 methods with a separate patch?

I've split and simplified the comments to be able to standalone. Also removed the reference to #885

[leejarvis]

@wolfgangw no problem, I think it's fine for now but since we're not supporting pre 1.9 using stuff like each_with_object where it's sensible makes sense. Thanks for the update, I'll merge this over the weekend.

[flavorjones]

Closing this. I'm sorry for this response, especially given the amount of time that has passed, but the use case of collect_namespaces is unclear to me, and I'd prefer not to increase the variations of methods unless and until I understand it.

Generally speaking, I'd love for a test case to illustrate how a method is going to be used when possible. I'm happy to entertain this PR again if someone can explain to me the use of this suite of methods around collecting namespaces.