Describe the PR

Fix a bug in ancestor node streams.

If you have an ancestor path like /B/B/A/A, where the innermost (last) node is named a, then
a.ancestors(B.class).drop(1) was equivalent to a.getParent().ancestors(B.class), which is wrong as it still contains both B nodes.

This also makes ancestor streams less lazy, so that they can be folded to empty streams more often.

Ready?

• Added unit tests for fixed bug/feature
• Passing all unit tests
• Complete build ./mvnw clean verify passes (checked automatically by travis)
• Added (in-code) documentation (if needed)