Python error on init() call after sleep() is called

[iago1460]

Traceback (most recent call last):
  ...
  File "/home/pi/workspace/waveshare_epd/epd7in5b_HD.py", line 76, in init
    if (epdconfig.module_init() != 0):
  File "/home/pi/workspace/waveshare_epd/epdconfig.py", line 71, in module_init
    self.SPI.max_speed_hz = 4000000
OSError: [Errno 9] Bad file descriptor

This looks like a regression bug. Applying the changes of #65 seems to work just fine.

[SSYYL]

Another approach is to separate sleep() and Dev_exit()