Fix error caused by keyboard module in blink detection example

Using the keyboard module in linux requires root permission and if virtual envs are used to run the script, it will produce the following error:

ImportError(You must be root to use this library on linux.)

To solve this, use OpenCV waitKey() functionality.

examples/blink_detection.py

@@ -15,7 +15,6 @@ import face_recognition
 import cv2
 import time
 from scipy.spatial import distance as dist
-import keyboard as kb
 
 EYES_CLOSED_SECONDS = 5
 
@@ -74,8 +73,9 @@ def main():
                     while (asleep): #continue this loop until they wake up and acknowledge music
                         print("EYES CLOSED")
 
-                        if (kb.is_pressed('space')):
+                        if cv2.waitKey(1) == 32: #Wait for space key  
                             asleep = False
+                            print("EYES OPENED")
                     closed_count = 0
 
         process = not process