Add support for pl 1.2

[oke-aditya]

Support PyTorch Lightning 1.2

[codecov]

Codecov Report

Merging #99 (e43c400) into master (29b497a) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master      #99   +/-   ##
=======================================
  Coverage   78.05%   78.05%           
=======================================
  Files          49       49           
  Lines        1581     1581           
=======================================
  Hits         1234     1234           
  Misses        347      347           

Flag	Coverage Δ
unittests	78.05% <ø> (ø)

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[oke-aditya]

Slow detr tests will be fixed in #86