Fixed ValueError when install on Windows

When install on Windows, it raise ValueError:

pip install qrcode -U
Downloading/unpacking qrcode
  Downloading qrcode-2.5.tar.gz
  Running setup.py egg_info for package qrcode
Installing collected packages: qrcode
  Running setup.py install for qrcode
    Traceback (most recent call last):
      File "<string>", line 1, in <module>
      
      ... 
      
              dir = convert_path(f[0])
      File "C:\Python26\lib\distutils\util.py", line 201, in convert_path
        raise ValueError, "path '%s' cannot end with '/'" % pathname
    ValueError: path 'share/man/man1/' cannot end with '/'
Merge pull request #24 from mozillazg/patch-1

Fix installation error on Windows