Add time crate support for Timestamp

[pbzweihander]

Description

{ describe your changes here }

Checklist

• [x] Formatted code using cargo fmt --all
• [x] Linted code using clippy
  • [x] with reqwest feature: cargo clippy --manifest-path influxdb/Cargo.toml --all-targets --no-default-features --features serde,derive,reqwest-client-rustls -- -D warnings
  • [x] with surf feature: cargo clippy --manifest-path influxdb/Cargo.toml --all-targets --no-default-features --features serde,derive,hyper-client -- -D warnings
• [ ] Updated README.md using cargo doc2readme -p influxdb --expand-macros
• [x] Reviewed the diff. Did you leave any print statements or unnecessary comments?
• [x] Any unfinished work that warrants a separate issue captured in an issue with a TODO code comment

[msrd0]

Thanks, adding time support is something I wanted to see for a long time but never got around to it!

I haven't actually checked where exactly we use chrono, but if it's only for the Timestamp, do you think you could make both chrono and time optional? I feel like most users wouldn't need both at the same time

[pbzweihander]

@msrd0 I've updated the PR!

[Empty2k12]

The tests need to be adapted to test both chrono and time independently. The tests should enable the features. Ci is currently failing since chrono could not be found in the test.

[msrd0]

The tests need to be adapted to test both chrono and time independently.

I'm not sure that's necessary. These two features don't seem to conflict each other.