Split logger.h into log_reader and log_writer

Much simpler!

Change-Id: I6c4ee363b56b67dac40c456261bbed79d01b8eb6
diff --git a/y2019/control_loops/drivetrain/BUILD b/y2019/control_loops/drivetrain/BUILD
index ed6d832..c21433b 100644
--- a/y2019/control_loops/drivetrain/BUILD
+++ b/y2019/control_loops/drivetrain/BUILD
@@ -232,7 +232,8 @@
         "//aos:init",
         "//aos/events:shm_event_loop",
         "//aos/events:simulated_event_loop",
-        "//aos/events/logging:logger",
+        "//aos/events/logging:log_reader",
+        "//aos/events/logging:log_writer",
         "//frc971/control_loops/drivetrain:drivetrain_lib",
         "@com_github_gflags_gflags//:gflags",
         "@com_github_google_glog//:glog",