Reformat code with Black

[mryab]

Adjusted the default configuration with 119 characters per line (this is the highest number allowed by GitHub PR view window).

Also, added pyproject.toml for configuring tools such as black/isort. However, compiling libp2p from scratch conflicts with the PEP517 build system backend, which is enabled by pyproject.toml: specifically, supplying build_py makes pip compile all dependencies from scratch (see pypa/pip#4118), which significantly increases the build time. To mitigate this issue, for now I supplied the --no-use-pep517 option to pip (see 5ef79da — without this change, the build works correctly, but we need to remove the timeout). This will likely be documented in #307, along with other considerations related to libp2p installation

[codecov]

Codecov Report

Merging #274 (f05083f) into master (4a33d1b) will decrease coverage by 0.08%.
The diff coverage is 77.56%.

@@            Coverage Diff             @@
##           master     #274      +/-   ##
==========================================
- Coverage   82.11%   82.02%   -0.09%     
==========================================
  Files          66       66              
  Lines        5893     5898       +5     
==========================================
- Hits         4839     4838       -1     
- Misses       1054     1060       +6     

Impacted Files	Coverage Δ
hivemind/averaging/group_info.py	100.00% <ø> (ø)
hivemind/hivemind_cli/run_server.py	0.00% <0.00%> (ø)
hivemind/moe/server/connection_handler.py	45.83% <0.00%> (ø)
hivemind/optim/adaptive.py	77.77% <0.00%> (ø)
hivemind/optim/base.py	71.42% <0.00%> (ø)
hivemind/optim/performance_ema.py	28.00% <ø> (ø)
hivemind/utils/limits.py	25.00% <ø> (ø)
hivemind/optim/collaborative.py	26.20% <8.33%> (ø)
hivemind/moe/server/task_pool.py	43.16% <28.57%> (ø)
hivemind/moe/server/runtime.py	74.77% <33.33%> (ø)
... and 50 more