Jack Fransham authored Apr 29, 2017 and Michael Aaron Murphy committed Apr 29, 2017

This is a pretty huge rework, replacing String with a custom SmallString
based on a SmallVec of bytes. Replacing newlines with spaces is now done
in-place, and most (for some value of "most") strings can now be stored
on the stack. This should reduce allocator load, but it also improves
cache locality. Whatever the real reason is, each of these changes
provides a real, measurable speed boost, and they combine to give an
improvement of something like 20-25%, meaning we're now 30-35% faster
than Dash. This is a breaking change, replacing some uses of String with
SmallString or &str in the public API, but I'm pretty sure no-one's
hooking into our public API anyway so that should be OK.