Remove py<3.3 backports and use pyproject.toml

[artemisart]

bz2file, backports.lzma are backports for py<3.3

[codecov[bot]]

Codecov Report

Patch and project coverage have no change.

Comparison is base (1681050) 98.10% compared to head (f173acf) 98.10%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #187 +/- ## ======================================= Coverage 98.10% 98.10% ======================================= Files 12 12 Lines 2380 2380 ======================================= Hits 2335 2335 Misses 45 45 ```

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.

[EntilZha]

LGTM, thanks!