Fix #84 (#87)

Make a list out of set, because vstack is not going to support non-sequence
input in the future.

Author: asiaszmek

kcsd/utility_functions.py

@@ -186,7 +186,7 @@ def check_for_duplicated_electrodes(elec_pos):
     -------
     has_duplicated_elec : Boolean
     """
-    unique_elec_pos = np.vstack({tuple(row) for row in elec_pos})
+    unique_elec_pos = np.vstack(list({tuple(row) for row in elec_pos}))
     has_duplicated_elec = unique_elec_pos.shape == elec_pos.shape
     return has_duplicated_elec