fix the scikit-image version to 0.14.0

For python3, scikit-image is automatically upgraded to 0.15.0, and the resize function in preprocessing will output different values as the previous versions:
https://github.com/foss-for-synopsys-dwc-arc-processors/synopsys-caffe/blob/master/python/caffe/io.py#L332 

test script (compare the python2 vs python3 results):
import caffe

transformer = caffe.io.Transformer({'data':(1, 3, 224, 224)})
img = caffe.io.load_image("/DATA/yche/cnn_models/caffe_models/images/ImageNet/jpeg/n01580077_10435.jpeg")
print(transformer.preprocess('data', img))

Author: vera121

python/requirements.txt

@@ -1,7 +1,7 @@
 Cython>=0.19.2
 numpy==1.15.4
 scipy==1.1.0
-scikit-image>=0.9.3
+scikit-image==0.14.4
 matplotlib>=1.3.1
 ipython>=3.0.0
 h5py>=2.2.0