Merge pull request #20 from mu40/numpy-warning

Fix NumPy deprecation warning.

surfa/core/framed.py

@@ -379,7 +379,7 @@ def percentile(self, percentiles, method='linear', nonzero=False):
         data = self.data
         if nonzero:
             data = data[data.nonzero()]
-        return np.percentile(data, percentiles, interpolation=method)
+        return np.percentile(data, percentiles, method=method)
 
     def clip(self, a_min, a_max):
         """