Allow to patch custom elements: changlog
# Changelog
[unreleased]
+- [BREAKING] Custom elements are now patched in-place (#364). Use `el_key` to force reinitialize an element.
- Added `el_key` method for adding keys to `El`s (#354).
- Enabled all additional markdown [extensions](https://docs.rs/pulldown-cmark/latest/pulldown_cmark/struct.Options.html).
- Removed `'static` bound from `El` and `Node`.
