Open example file in text mode.

examples/download_observations.py

@@ -18,7 +18,7 @@
         observations = download_observations(observer_code)
         print('All done.\nDownloaded %d observations.' % len(observations))
         filename = '%s.txt' % observer_code
-        with open(filename, 'wb') as fp:
+        with open(filename, 'w') as fp:
             writer = VisualFormatWriter(fp, observer_code)
             for observation in observations:
                 writer.writerow(observation)