Wren 0.6.4

Wren 0.6.4 keeps fixed headers in place while a page is busy, and removes a feature that never ran.

This is still a beta, under development, and Windows-only.

Fixed and sticky boxes while a page is busy. When a script keeps the interface thread and the wheel scrolls the kept picture of the page, a fixed header or a sticky box (Bootstrap's documentation header) stays where the page drew it, instead of sliding with the picture and jumping back.
No more partial redraw. browser.gpu.partial_redraw never ran on a window; the compositor no longer hashes every chunk at every frame for it.
setAttribute with the same value changes nothing in the document: observers still see the write, but there is no restyle and no layout.
Tests. The end-to-end sessions that drive a Wren run on a developer's machine, not on the shared runner; the release workflow no longer runs the tests again.

#Wren 0.6.4