Fix incorrect model name that breaks semantic segmentation demo (#284)

Author: wydwww

experiments/segmentation/demo.py

@@ -2,7 +2,7 @@
 import encoding
 
 # Get the model
-model = encoding.models.get_model('fcn_resnet50_ade', pretrained=True).cuda()
+model = encoding.models.get_model('fcn_resnet50s_ade', pretrained=True).cuda()
 model.eval()
 
 # Prepare the image