Removed sys.path hack in test, fixed spelling of import in __init__.py

skimage/exposure/__init__.py

@@ -1,3 +1,3 @@
 from .exposure import histogram, equalize, cumulative_distribution
 from .exposure import rescale_intensity
-from ._adaphist import adapthist
+from ._adapthist import adapthist

skimage/exposure/tests/test_exposure.py

@@ -1,7 +1,5 @@
 import numpy as np
 from numpy.testing import assert_array_almost_equal as assert_close
-import sys
-sys.path.insert(0, '../..')
 import skimage
 from skimage import data
 from skimage import exposure