Refactor linear_system out of 2017 intake

So we can reuse it!

Change-Id: I0583dbd1fd1a8765468f861a9acba0194aaa8ef6
diff --git a/y2017/control_loops/python/BUILD b/y2017/control_loops/python/BUILD
index 5d7a002..3f23bde 100644
--- a/y2017/control_loops/python/BUILD
+++ b/y2017/control_loops/python/BUILD
@@ -86,11 +86,9 @@
     restricted_to = ["//tools:k8"],
     deps = [
         ":python_init",
-        "//aos/util:py_trapezoid_profile",
         "//external:python-gflags",
         "//external:python-glog",
-        "//frc971/control_loops/python:controls",
-        "@matplotlib",
+        "//frc971/control_loops/python:linear_system",
     ],
 )