Use Mixin suffix

was using mixin concept, but the suffix makes pylint happier

Author: petercorke

roboticstoolbox/robot/DHDynamics.py

@@ -31,7 +31,7 @@ def wrapper_check_rne(*args, **kwargs):
     return wrapper_check_rne
 
 
-class DHDynamics:
+class DHDynamicsMixin:
 
     def printdyn(self):
         """

roboticstoolbox/robot/DHRobot.py

@@ -16,11 +16,11 @@
 from roboticstoolbox.backends.PyPlot.functions import \
     _plot, _teach, _fellipse, _vellipse, _plot_ellipse, \
     _plot2, _teach2
-from roboticstoolbox.robot.DHDynamics import DHDynamics
+from roboticstoolbox.robot.DHDynamics import DHDynamicsMixin
 from ansitable import ANSITable, Column
 
 
-class DHRobot(Robot, DHDynamics):
+class DHRobot(Robot, DHDynamicsMixin):
     """
     Class for robots defined using Denavit-Hartenberg notation