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/y2012/control_loops/python/drivetrain.py b/y2012/control_loops/python/drivetrain.py
index 7e672e3..5449503 100755
--- a/y2012/control_loops/python/drivetrain.py
+++ b/y2012/control_loops/python/drivetrain.py
@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/python3
 
 from __future__ import print_function
 from frc971.control_loops.python import drivetrain
diff --git a/y2012/control_loops/python/polydrivetrain.py b/y2012/control_loops/python/polydrivetrain.py
index efe4511..ae26dbe 100755
--- a/y2012/control_loops/python/polydrivetrain.py
+++ b/y2012/control_loops/python/polydrivetrain.py
@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/python3
 
 import sys
 from y2012.control_loops.python import drivetrain