Add QElidingLabel (#16)

* wip

* single class implementation

* fix init

* improve implementation

* improve sizeHint

* wrap

* update docs

* rename

* remove overloads

* review changes

* docs and reformat

* remove width from _elided text

* add tests

examples/eliding_label.py

@@ -0,0 +1,12 @@
+from superqt import QElidingLabel
+from superqt.qtcompat.QtWidgets import QApplication
+
+app = QApplication([])
+
+widget = QElidingLabel(
+    "a skj skjfskfj sdlf sdfl sdlfk jsdf sdlkf jdsf dslfksdl sdlfk sdf sdl "
+    "fjsdlf kjsdlfk laskdfsal as lsdfjdsl kfjdslf asfd dslkjfldskf sdlkfj"
+)
+widget.setWordWrap(True)
+widget.show()
+app.exec_()