pep8 and typo fixes

Author: sprenger

neo/io/asciisignalio.py

@@ -208,7 +208,7 @@ def read_segment(self, lazy=False):
                 sig = sig[:, mask]
         elif self.method == 'homemade':
             with open(self.filename, 'r', newline=None) as fid:
-                for l in range(self.skiprows):
+                for _ in range(self.skiprows):
                     fid.readline()
                 tab = []
                 for line in fid.readlines():

neo/io/tiffio.py

@@ -108,7 +108,8 @@ def natural_sort(l):
         if len(list_data_image.shape) == 4:
             list_data_image = []
             for file_name in file_name_list:
-                data = np.array(Image.open(self.filename + "/" + file_name).convert('L')).astype=np.float32
+                image = Image.open(self.filename + "/" + file_name).convert('L')
+                data = np.array(image).astype(np.float32)
                 list_data_image.append(data)
 
         print("read block")