Add a finalizer to prevent memory leaks

[nhz2]

Fixes #27

This PR uses atomic operations to prevent multiple finalizers from freeing the same stream concurrently.

This requires julia 1.7

[codecov]

Codecov Report

Attention: Patch coverage is 80.00000% with 19 lines in your changes missing coverage. Please review.

Project coverage is 87.15%. Comparing base (95a9fc8) to head (01df96f).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
src/compression.jl	77.77%	10 Missing ⚠️
src/decompression.jl	82.00%	9 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #42      +/-   ##
==========================================
+ Coverage   82.63%   87.15%   +4.51%     
==========================================
  Files           4        4              
  Lines         167      179      +12     
==========================================
+ Hits          138      156      +18     
+ Misses         29       23       -6     

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