Add JUnitXML.fromroot

[EnricoMi]

This allows to create an JUnitXML instance from an ElementTree root element, just like parsing a file.

Use case: I have parsed a file into an ElementTree and performed some operations on that tree. From the final tree, I want to create the JUnitXML object, identical to JUnitXML.fromfile and JUnitXML.fromstring.

There is some extra logic in JUnitXML.fromfile and JUnitXML.fromstring, that is not in Element.fromelem.

[codecov]

Codecov Report

Merging #92 (2754098) into master (7faf99f) will decrease coverage by 0.93%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master      #92      +/-   ##
==========================================
- Coverage   99.45%   98.52%   -0.94%     
==========================================
  Files           4        6       +2     
  Lines        1102     1218     +116     
==========================================
+ Hits         1096     1200     +104     
- Misses          6       18      +12     

Impacted Files	Coverage Δ
junitparser/junitparser.py	99.14% <100.00%> (+0.02%)	⬆️
tests/test_general.py	100.00% <100.00%> (ø)
junitparser/cli.py	53.84% <0.00%> (ø)
tests/test_cli.py	100.00% <0.00%> (ø)

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[weiwei]

Thanks for the PR!

[EnricoMi]

Thanks!