Fix logic for detection of Windows OS (#42)

Should be `if os.name == 'nt'`, and *not* `if sys.platform == 'nt'`.
Helpful explanation at https://stackoverflow.com/a/11674977/20789.

Signed-off-by: Daniel Lenski <dlenski@gmail.com>

Author: zepc007

zxing/__init__.py

@@ -42,7 +42,7 @@ def __init__(self, message, filename=None):
 
 class BarCodeReader(object):
     cls = "com.google.zxing.client.j2se.CommandLineRunner"
-    classpath_sep = ';' if sys.platform == 'nt' else ':'  # https://stackoverflow.com/a/60211688
+    classpath_sep = ';' if os.name == 'nt' else ':'  # https://stackoverflow.com/a/60211688
 
     def __init__(self, classpath=None, java=None):
         self.java = java or 'java'