remove chrono dependency

[coderedart]

when i run cargo audit, i get this error

Crate:     time
Version:   0.1.45
Title:     Potential segfault in the time crate
Date:      2020-11-18
ID:        RUSTSEC-2020-0071
URL:       https://rustsec.org/advisories/RUSTSEC-2020-0071
Severity:  6.2 (medium)
Solution:  Upgrade to >=0.2.23
Dependency tree:
time 0.1.45
└── chrono 0.4.26
    └── arcdps 0.9.0
        └── jokolink 0.1.0
error: 1 vulnerability found!

chrono won't fix it chronotope/chrono#602 (comment)
and instead recommends people to wait for 0.5 release which has been going on since April chronotope/chrono#970 . Just like the Alliances :D

So, we have three options:

1. wait for chrono 0.5 which might take a while
2. directly use time crate, if possible.
3. feature gate the uses of chrono. AFAIK it is only used for combat messages. and they can be enabled by an optional feature

[greaka]

Chrono won't fix it because they aren't affected. As a result, I'm not in a hurry to fix it either. Feel free to open a PR though 🙂

[pitdicker]

The plan for chrono is to release a 0.4 version soon (I hope within weeks) that drops the time 0.1 dependency. It has been part of the public API, that is why it took so long. But we don't believe making the switch now would cause real-world breakage.

[greaka]

cargo update fixes this issue
https://github.com/chronotope/chrono/releases/tag/v0.4.30