Use Enumerable

[cfis]

This commit removes the custom iteration methods in the Cursor class and instead switches to Ruby's Enumerable module.

This is a backwards incompatible change because it required renaming find_all to find_by_kind (find_all is an enumerable method). In addition, the function signature changed to allow the caller to specify whether to search direct children or all children.

Also it renames visit_children to each. The each method now takes an optional parameter that specifies whether to recurse through the tree or not. By default it is true to match the previous behavior. Note you can only set this when using each, and not when using other Enumerable methods since there is now way to pass it through filter, select, etc. Also note blocks passed to the methods receive two parameters, child and parent, which might be confusing to some people (although it is like iterating through a Hash).

For my particular use case, I want to be able to control whether iteration is recursive or not.

Thoughts?

[ioquatix]

It seems okay to me.

It's okay to leave specialised implementations if they can be more efficient than the generic implementations provided by Enumerable.