[plot] ImageData object has no attribute getRbgaImageData
I was trying to save the plot as a PNG image.
It have to be investigated, but it is part of the silx release 0.5.

```
Traceback (most recent call last):
  File "/home/valls/.local/lib/python2.7/site-packages/silx/gui/plot/PlotActions.py", line 830, in _actionTriggered
    return self._saveImage(filename, nameFilter)
  File "/home/valls/.local/lib/python2.7/site-packages/silx/gui/plot/PlotActions.py", line 762, in _saveImage
    rgbaImage = image.getRbgaImageData(copy=False)
AttributeError: 'ImageData' object has no attribute 'getRbgaImageData'
```
diff --git a/silx/gui/plot/PlotActions.py b/silx/gui/plot/PlotActions.py
index 5fec51d0b..42abd68af 100644
--- a/silx/gui/plot/PlotActions.py
+++ b/silx/gui/plot/PlotActions.py
@@ -759,7 +759,7 @@ class SaveAction(PlotAction):
         elif nameFilter in (self.IMAGE_FILTER_RGB_PNG,
                             self.IMAGE_FILTER_RGB_TIFF):
             # Get displayed image
-            rgbaImage = image.getRbgaImageData(copy=False)
+            rgbaImage = image.getRgbaImageData(copy=False)
             # Convert RGB QImage
             qimage = convertArrayToQImage(rgbaImage[:, :, :3])
 
['silx/gui/plot/PlotActions.py']