Change to s3boto monkeypatch to allow no auth

Change to s3boto monkeypatch to allow no auth - course images and
instructor photos shouldn't have auth strings

Fixed typo for attachment
Merge pull request #2316 from dglance/dglance-s3boto-url

Change to s3boto monkeypatch to allow no auth
Documentation fixes on s3boto monkeypatch
Merge pull request #2318 from Stanford-Online/jrbl-monkeypatch-docfixes

Documentation fixes on s3boto monkeypatch