add -ex to #! to echo lines and abort if anything errors

when I ran sudo ./install, something erred, but it got buried under the output from rest of the script.
-e will abort on error
-x will echo the lines of the script so we can see what line errored.

install

@@ -1,4 +1,4 @@
-#!/bin/bash
+#!/bin/bash -ex
 # Graphite installation script for Ubuntu 13.10 x64
 # Jason Dixon <[email protected]>