Firecracker v0.18.0

Added

• New device: virtio-vsock, backed by Unix domain sockets (GitHub issue #650).
  See docs/vsock.md.

Fixed

• Updated the documentation for integration tests.
• Fixed high CPU usage before guest network interface is brought up (GitHub
  issue #1049).
• Fixed an issue that caused the wrong date (month) to appear in the log.
• Fixed a bug that caused the seccomp filter to reject legit syscalls in some
  rare cases (GitHub issue #1206).
• Docs: updated the production host setup guide.
• Docs: updated the rootfs and kernel creation guide.

Removed

• Removed experimental support for vhost-based vsock devices.