`SystemTime::elapsed()` is broken

[justinlovinger]

self.duration_since(SystemTime::now()), https://github.com/sebcrozet/instant/blob/master/src/wasm.rs#L202, should be Self::now().duration_since(*self), like Instant.

[FrankReh]

@sebcrozet Would you accept a PR for this? This was introduced in PR #42. The std implementation for SystemTime::elapsed is also like @justinlovinger points out: https://github.com/rust-lang/rust/blob/109cccbe4f345c0f0785ce860788580c3e2a29f5/library/std/src/time.rs#L554-L556

[MingweiSamuel]

Wow this crate is so amazingly busted

[sebcrozet]

This is now fixed in version 0.1.13.
I have now marked the crate as unmaintained in the readme and cargo badge.