support passing profile data though PIPE, by reopen fd=2 if stdin is not a tty.

[laixintao]

close #4

[codecov-commenter]

Codecov Report

Merging #35 (ef75c0b) into main (db14a48) will increase coverage by 0.35%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main      #35      +/-   ##
==========================================
+ Coverage   68.09%   68.45%   +0.35%     
==========================================
  Files          13       13              
  Lines         815      821       +6     
==========================================
+ Hits          555      562       +7     
+ Misses        260      259       -1     

Files	Coverage Δ
flameshow/main.py	97.72% <100.00%> (+0.50%)	⬆️
flameshow/render/flamegraph.py	41.40% <ø> (-0.08%)	⬇️

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