2.0 - New major version

Say hello to this new version! 👋

• Drop PHP5 support (BC break) - #12
• Functions are now namespaced (BC break) - #13
• Removed is_iterable function, as it's now PHP7+ native
• Removed withMap() and withFilter() methods of fluent interface in favor of map() and filter() - #9 (BC break)
• Added iterable_values() function - #33
• Allow objects as keys - #24
• Add support for default filter function - #25

A huge thanks to @simPod for his contributions! 🙏