Fix duplicate file name extension

nattress · nattress · commit defa89d34e8b · 2014-11-29T13:13:49.000-08:00
If a filename extension and a format are specified with the same string,
we create a file with a double file extension. Ie:

```javascript
py.image.save_as(figure, 'filename2.png', 'png')
```
This will produce a file named filename2.png.png. When ext and format
are both present, the fix will only append format to the filename if the
format is different from ext. Ie:
```javascript
py.image.save_as(figure, 'filename2.png', 'pdf')
```
This will create filename2.png.pdf.
diff --git a/plotly/plotly/plotly.py b/plotly/plotly/plotly.py
@@ -660,7 +660,7 @@ def save_as(cls, figure_or_data, filename, format=None, width=None, height=None)
             format = ext[1:]
         elif not ext and format:
             filename += '.'+format
-        else:
+        elif ext[1:].lower() != format.lower():
             filename += '.'+format
 
         img = cls.get(figure_or_data, format, width, height)
