v0.3.1

• Bug fixes
  • Move ntpd's prints to the log. The previous prints to the console were quite
    annoying to say the least.
  • Remove the build timestamp so that nerves_time builds are reproducible.
    This is important for users that want to recreate firmware images with as
    few differences as possible. The build timestamp had restricted the earliest
    allowed time. The earliest time is now hardcoded, but can be overridden by
    application config (same with the latest possible time.)