Replace chrono with time 0.3 for cargo audit reports

[sunng87]

The current release chrono depends on time 0.1.x, which has an issue reported by cargo audit. Also chrono doesn't seem to be well maintained. Its latest version was released 16 months ago. time 0.3.x provides similar functionalities to chrono and could be a good replacement for it.

[msrd0]

Oops, chrono should not depend on time 0.1. I hate that that's enabled by default.