Update pyglet from 1.3.0 to 1.3.1

requirements.txt

 pluggy==0.6.0
 psutil==5.4.3
 py==1.5.2
-pyglet==1.3.0
+pyglet==1.3.1
 pytest==3.3.2
 python-dateutil==2.6.1
 PyYAML==3.12