Make matplotlib targets depend on gtk

Otherwise matplotlib complains it has no graphical backend and won't pop
up a plot.

Change-Id: I73b024c957ea87d1f440f1b73f0806440655c0fd
Signed-off-by: Austin Schuh <austin.linux@gmail.com>
diff --git a/y2016/control_loops/python/BUILD b/y2016/control_loops/python/BUILD
index ad3fbe9..6b54950 100644
--- a/y2016/control_loops/python/BUILD
+++ b/y2016/control_loops/python/BUILD
@@ -61,6 +61,7 @@
         "//frc971/control_loops/python:controls",
         "@pip//glog",
         "@pip//matplotlib",
+        "@pip//pygobject",
         "@pip//python_gflags",
     ],
 )
@@ -94,6 +95,7 @@
         "//frc971/control_loops/python:controls",
         "@pip//glog",
         "@pip//matplotlib",
+        "@pip//pygobject",
         "@pip//python_gflags",
     ],
 )
@@ -111,6 +113,7 @@
         "//frc971/control_loops/python:controls",
         "@pip//glog",
         "@pip//matplotlib",
+        "@pip//pygobject",
         "@pip//python_gflags",
     ],
 )
@@ -140,6 +143,7 @@
         "//frc971/control_loops/python:controls",
         "@pip//glog",
         "@pip//matplotlib",
+        "@pip//pygobject",
         "@pip//python_gflags",
     ],
 )
@@ -157,6 +161,7 @@
         "//frc971/control_loops/python:controls",
         "@pip//glog",
         "@pip//matplotlib",
+        "@pip//pygobject",
         "@pip//python_gflags",
     ],
 )