BUG: fix reference to the list being edited.
Fix Qt TreeEditor to honor node background color.

The code was misplaced, likely due to a bad merge.
Qt TreeEditor: Initialize column labels for node.

Previously, only listeners for column labels were attached
but the initial value of column labels was not being set.
Merge pull request #131 from pankajp/qt-treeeditor-node-background-color-bad-merge

Fix Qt TreeEditor to honor node bg/fg colors and column labels.
Merge pull request #130 from enthought/fix/qt4-list-str-editor-values

BUG: fix reference to the list being edited.
Merge branch 'master' into fix/qt-tabular-drag