Fix #749, #620: implement lchown()

[andrewkoung]

Let me know if my logic was wrong, but I believe this was the correct flow.

[codecov-io]

Codecov Report

Merging #752 into master will increase coverage by 0.03%. The diff coverage is 87.09%.

@@            Coverage Diff             @@
##           master     #752      +/-   ##
==========================================
+ Coverage   86.88%   86.92%   +0.03%     
==========================================
  Files          16       16              
  Lines        1739     1751      +12     
==========================================
+ Hits         1511     1522      +11     
- Misses        228      229       +1

Impacted Files	Coverage Δ
src/filesystem/interface.js	93.29% <ø> (ø)	:arrow_up:
src/filesystem/implementation.js	84.21% <87.09%> (+0.08%)	:arrow_up:

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[humphd]

Updated the title of this PR, since it will fix #749, #620.

[andrewkoung]

There happens to be a test for chown() already, but I've created the test for lchown()!