replacing ListItemAttr with ItemAttr to avoid deprecation warning

[aaronayres35]

See comments on #667.

We do not currently see the deprecation warning when using a wx environment created by the etstool in pyface as the development environment has pinned an older version of wxPython.
However, when using an environment with newer wx, there was the following deprecation warning (found when running the explorer.py example):

/Users/aayres/Desktop/pyface/pyface/ui/wx/viewer/table_viewer.py:313: wxPyDeprecationWarning: Using deprecated class. Use ItemAttr instead
  self._even_row_attribute = wx.ListItemAttr()
/Users/aayres/Desktop/pyface/pyface/ui/wx/viewer/table_viewer.py:318: wxPyDeprecationWarning: Using deprecated class. Use ItemAttr instead
  self._odd_row_attribute = wx.ListItemAttr()

[aaronayres35]

CI is failing, I'm not sure why. I will try to look into this later today

[kitchoi]

Thank you @aaronayres35!

[corranwebster]

Wx failure appears unrelated, but we've been getting a lot of linux/wx failures on multiple PRs. I've set the test to re-run, but if this continues, we may need to dig in a bit (or mark linux/wx test suites as being allowed to fail for CI to pass).

[kitchoi]

@rahulporuri spotted a version mismatch between Ubuntu version on Travis and the one targeted by the wxPython wheel used for CI. It might be related (or it might not be...)
#669 (comment)

[codecov-commenter]

Codecov Report

Merging #670 into master will increase coverage by 0.21%.
The diff coverage is 75.00%.

@@            Coverage Diff             @@
##           master     #670      +/-   ##
==========================================
+ Coverage   39.16%   39.37%   +0.21%     
==========================================
  Files         491      491              
  Lines       26911    26958      +47     
  Branches     4067     4085      +18     
==========================================
+ Hits        10539    10615      +76     
+ Misses      15906    15890      -16     
+ Partials      466      453      -13     

Impacted Files	Coverage Δ
pyface/ui/wx/viewer/table_viewer.py	0.00% <0.00%> (ø)
pyface/util/testing.py	88.57% <ø> (ø)
pyface/__init__.py	88.88% <90.00%> (ø)
pyface/ui/qt4/console/console_widget.py	29.28% <0.00%> (+0.41%)	⬆️
pyface/ui/qt4/code_editor/code_widget.py	44.16% <0.00%> (+0.42%)	⬆️
pyface/ui/qt4/tasks/split_editor_area_pane.py	65.41% <0.00%> (+0.59%)	⬆️
pyface/ui/qt4/tasks/advanced_editor_area_pane.py	51.72% <0.00%> (+0.86%)	⬆️
pyface/ui/qt4/tasks/editor_area_pane.py	55.88% <0.00%> (+2.20%)	⬆️
pyface/ui/qt4/application_window.py	91.66% <0.00%> (+2.38%)	⬆️
... and 5 more

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[kitchoi]

LGTM