Add scripts to print and log I2C hangs.

usb/log-i2c-hangs.sh

@@ -0,0 +1,3 @@
+#!/bin/bash
+
+./print-i2c-hangs.sh > i2c-hangs-`date +%Y-%m-%d_%H:%M:%S`.log

usb/print-i2c-hangs.sh

@@ -0,0 +1,11 @@
+#!/bin/bash
+
+while true; do
+    startSeconds=`date +%s`
+    ./wait-until-i2c-dies.js
+    endSeconds=`date +%s`
+    elapsedSeconds=$((startSeconds-endSeconds))
+    echo $elapsedSeconds
+    ./jump-to-bootloader.js > /dev/null
+    sleep 6
+done