Enforce gofmt in travis

Run gofmt -l . during travis to catch pull requests that have not had
gofmt run on them.

Change-Id: Ibfdf988a535d82721f3c4bc328b189f606f12778
diff --git a/.travis.gofmt.sh b/.travis.gofmt.sh
new file mode 100755
index 0000000..3aa9374
--- /dev/null
+++ b/.travis.gofmt.sh
@@ -0,0 +1,7 @@
+#!/bin/bash
+
+if [ -n "$(gofmt -l .)" ]; then
+    echo "Go code is not formatted:"
+    gofmt -d .
+    exit 1
+fi