failIf, takeIf, dynamicTraversal

What's Changed

• dynamic breadth- and depth-first traversal by @robstoll in #200
• takeIf as prefix operation by @robstoll in #201
• move default peeking iterator by @robstoll in #202 => breaking change, use PeekingIterator to create an instance
• add failIf by @robstoll in #204

Full Changelog: v1.0.0...v1.1.0