Added an import of median from the filters module

(it's `filters.rank.median`, but it is convenient to have the very common
median filter in `filters` as well)

skimage/filters/__init__.py

@@ -8,6 +8,7 @@ from ._gabor import gabor_kernel, gabor_filter
 from .thresholding import (threshold_adaptive, threshold_otsu, threshold_yen,
                            threshold_isodata)
 from . import rank
+from .rank import median
 
 from skimage._shared.utils import deprecated
 from skimage import restoration
@@ -30,6 +31,7 @@ __all__ = ['inverse',
            'wiener',
            'LPIFilter2D',
            'gaussian_filter',
+           'median',
            'canny',
            'sobel',
            'hsobel',

skimage/filters/tests/test_filter_import.py

@@ -1,5 +1,6 @@
 from warnings import catch_warnings, simplefilter
 
+from skimage.filters import median
 
 def test_filter_import():
     with catch_warnings():