Using Pickle 5 by default for both cache and hashing

[Vopaaz]

Pickle protocol 5 has built-in ability to efficiently handle large data. Switch to use this as default to optimize memory usage.

[codecov]

Codecov Report

Merging #4 (e1e10c1) into master (994d4a2) will decrease coverage by 0.18%.
The diff coverage is 96.15%.

@@            Coverage Diff             @@
##           master       #4      +/-   ##
==========================================
- Coverage   96.93%   96.75%   -0.19%     
==========================================
  Files          26       24       -2     
  Lines         554      554              
  Branches       75       77       +2     
==========================================
- Hits          537      536       -1     
- Misses          9       12       +3     
+ Partials        8        6       -2     

Impacted Files	Coverage Δ
checkpointing/__init__.py	100.00% <ø> (ø)
checkpointing/hash/stream.py	86.95% <86.95%> (ø)
checkpointing/cache/pickle_file.py	100.00% <100.00%> (ø)
checkpointing/config.py	100.00% <100.00%> (ø)
checkpointing/decorator/base.py	100.00% <100.00%> (ø)
checkpointing/hash/__init__.py	100.00% <100.00%> (ø)
checkpointing/hash/generic.py	100.00% <100.00%> (ø)
checkpointing/identifier/func_call/context.py	100.00% <100.00%> (ø)
checkpointing/logging/__init__.py	100.00% <100.00%> (ø)
checkpointing/util/pickle.py	100.00% <100.00%> (ø)

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