Support a new `relative_include` tag
Trash the subclass
Rename tag to `include_relative`
Define methods for shared vars between include & include_relative
Separate include_relative test out into its own context
Test that includes relative to self are included
Add tests around nasty include attempts
Add documentation on the include_relative tag
Rename method to `resolved_includes_dir`
Sanitize the resolved includes path
Merge pull request #2870 from gjtorikian/support-relative-include
Update history to reflect merge of #2870 [ci skip]
Update include_relative tests

This verifies you can’t go “up” in the include
Add some more docs on `include_relative`
Set tag name as ivar

This lets us use just one syntax_example method for both classes.
Fixing "vertycal" typo

s/vertycal/vertical

Unless, like, "vertycal" was on purpose or something.
Merge pull request #2889 from pdehaan/patch-1
Update history to reflect merge of #2889 [ci skip]
Merge pull request #2884 from gjtorikian/improve-docs-for-include-relative
Update history to reflect merge of #2884 [ci skip]