v2.5.2

• release v2.5.2
• improved parameter checkng, the error msg more detail.
• new class MycobotCommandGenerator that generate binary real command.

  from pymycobot import MycobotCommandGenerator
  mg = MycobotCommandGenerator()
  print(mg.get_angles())
  print(mg.power_on())
  
  >>> ([254, 254, 2, 32, 250], True)
  >>> ([254, 254, 2, 16, 250], False)

• can import needed class from pymycobot, like:

  from pymycobot import Mycobot, Angle, Coord, MycobotCommandGenerator

• Fixed python2 compatibility issue.