Allow installing only TF or torch version

[gitanshu]

No description provided.

[codecov]

Codecov Report

Merging #2155 (5bd4d70) into master (62bbc5c) will decrease coverage by 0.29%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #2155      +/-   ##
==========================================
- Coverage   91.79%   91.49%   -0.30%     
==========================================
  Files         242      197      -45     
  Lines       17456    10845    -6611     
  Branches     2534     1356    -1178     
==========================================
- Hits        16024     9923    -6101     
+ Misses       1063      666     -397     
+ Partials      369      256     -113     

Impacted Files	Coverage Δ
src/garage/torch/algos/pearl.py	48.29% <0.00%> (-31.35%)	⬇️
src/garage/tf/_functions.py	55.12% <0.00%> (-19.71%)	⬇️
src/garage/envs/multi_env_wrapper.py	79.51% <0.00%> (-14.60%)	⬇️
src/garage/tf/policies/policy.py	77.77% <0.00%> (-13.53%)	⬇️
src/garage/sampler/env_update.py	82.92% <0.00%> (-13.08%)	⬇️
src/garage/tf/algos/erwr.py	44.44% <0.00%> (-12.70%)	⬇️
src/garage/experiment/task_sampler.py	75.86% <0.00%> (-7.58%)	⬇️
...rage/tf/optimizers/conjugate_gradient_optimizer.py	81.90% <0.00%> (-6.57%)	⬇️
src/garage/plotter/plotter.py	62.06% <0.00%> (-5.46%)	⬇️
src/garage/experiment/meta_evaluator.py	88.63% <0.00%> (-5.12%)	⬇️
... and 162 more

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[ryanjulian]

Do the tests pass under these configurations? Maybe at least run a pylint on both configs (it should detect importerrors)