Switch to python3 and scipy from slycot

Turns out we need python3 matplotlib to make scipy work well enough to
place the poles correctly for our systems.  Rather than do it piecemeal,
do it all at once.

This includes a python opencv upgrade too to support the new python, and
a matplotlib upgrade.

Change-Id: Ic7517b5ebbfdca9cc90ae6a61d86b474f2f21b29
diff --git a/y2016/control_loops/python/shooter.py b/y2016/control_loops/python/shooter.py
index 5e3eddb..70af1b0 100755
--- a/y2016/control_loops/python/shooter.py
+++ b/y2016/control_loops/python/shooter.py
@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/python3
 
 from frc971.control_loops.python import control_loop
 from frc971.control_loops.python import controls