Add aiofiles.os.readlink function

[jpy-git]

Following up on the symlink PR #124 this PR adds the aiofiles.os.readlink function to retrieve the symlinked path from the symlink.

Docs: https://docs.python.org/3/library/os.html#os.readlink

Added a test case.

[codecov-commenter]

Codecov Report

Merging #125 (d609474) into master (313f4a5) will increase coverage by 0.03%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #125      +/-   ##
==========================================
+ Coverage   89.73%   89.76%   +0.03%     
==========================================
  Files          10       10              
  Lines         302      303       +1     
==========================================
+ Hits          271      272       +1     
  Misses         31       31              

Impacted Files	Coverage Δ
src/aiofiles/os.py	100.00% <100.00%> (ø)

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[Tinche]

Thanks!