Adding a code snippet to the landing page.

[dhermes]

NOTE: Has #661 as a diffbase

Fixes#646 (originally I accidentally said #553).

Uses the Python snippet

fromgcloudimportdatastoredatastore.set_defaults()
product_key=datastore.Key('Product', 123)
printdatastore.get([product_key])

and

pygmentize -f html gcloud_landing_snippet.py

to create the highlighted HTML.

I initially tried to find a place to put these, but the nothing really felt appropriate since the main index.html is not part of any build stage.

[tseaver]

c5935da LGTM

[dhermes]

Rebased, merging now.