Run jiri's bootstrap_jiri script in bootstrap.sh.
Run jiri's bootstrap_jiri script in bootstrap.sh.

The old instructions about cloning the manifest directly are not going
to be supported much longer.

This CL updates the instructions to use the bootsrap_jiri script.

Change-Id: If2748b0f64eddd34997409658f459c77f326de9f

vanadium/website,vanadium/website,vanadium/website