playground: cleanup Dockerfile, unused field and add TODO

Change-Id: I018aecf12f4694de6f215a2dbbbfb7a09d6b2f5b
diff --git a/sandbox/Dockerfile b/sandbox/Dockerfile
index ee0a0a0..9247ac8 100644
--- a/sandbox/Dockerfile
+++ b/sandbox/Dockerfile
@@ -10,8 +10,9 @@
 RUN patch /usr/src/go/src/runtime/rt0_nacl_amd64p32.s /usr/src/go/enable-fake-time.patch
 
 # build go nacl tool chain
+# TODO(proppy): add fake filesystem
 RUN cd /usr/src/go/src && GOOS=nacl GOARCH=amd64p32 ./make.bash --no-clean
-RUN cd /usr/local/bin && curl -s -O https://storage.googleapis.com/gobuilder/sel_ldr_x86_64 && chmod +x sel_ldr_x86_64
+RUN cd /usr/local/bin && curl -s -O https://storage.googleapis.com/gobuilder/sel_ldr_x86_64 && chmod 0755 sel_ldr_x86_64
 
 # add and compile sandbox daemon
 ADD . /go/src/sandbox/
diff --git a/sandbox/play.go b/sandbox/play.go
index 8679945..251553c 100644
--- a/sandbox/play.go
+++ b/sandbox/play.go
@@ -16,7 +16,6 @@
 type Event struct {
 	Message string
 	Delay   time.Duration // time to wait before printing Message
-	Kind    string
 }
 
 // Decode takes an output string comprised of playback headers, and converts