Move tox to test requirements

[suzil]

• Sorted the test requirements to make it a bit easier to read
• Since we already have a setup.cfg file, move .coveragerc contents to it. I think since the setup.cfg file is there, coverage might've not even been reading the .coveragerc file, but I'm not sure. Either way, it's good to combine the files and move CI config settings all to one place

[codecov[bot]]

Codecov Report

Merging #383 into master will not change coverage. The diff coverage is n/a.

@@          Coverage Diff           @@
##           master    #383   +/-   ##
======================================
  Coverage    60.3%   60.3%           
======================================
  Files          78      78           
  Lines        6145    6145           
  Branches      809     809           
======================================
  Hits         3706    3706           
+ Misses       2265    2264    -1     
- Partials      174     175    +1

Impacted Files	Coverage Δ
frontera/contrib/backends/hbase/__init__.py	68.22% <0%> (ø)	:arrow_up:

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[suzil]

closing as no response