SensorReader PWM Refactor.

Refactored the pwm trigger and pwm detecter out of the year specific.

Change-Id: Ie89332fe6e1bcc0f465b742055ec4cf392a20c7e
diff --git a/frc971/wpilib/BUILD b/frc971/wpilib/BUILD
index bc3ac04..910de08 100644
--- a/frc971/wpilib/BUILD
+++ b/frc971/wpilib/BUILD
@@ -276,3 +276,20 @@
         "//aos/logging",
     ],
 )
+
+cc_library(
+    name = "sensor_reader",
+    srcs = [
+        "sensor_reader.cc",
+    ],
+    hdrs = [
+        "sensor_reader.h"
+    ],
+    restricted_to = ["//tools:roborio"],
+    deps = [
+        "//aos:init",
+        "//aos/time:time",
+        "//aos/stl_mutex",
+        "//third_party:wpilib",
+    ],
+)