Return html safe strings from rendering methods that have more than one tag.

Squashed commit of the following:

commit 3594d5c8d9d8dfd06c8c9256e52d06fc89a06966
Author: Daniel Pehrson <dpehrson@qurve.com>
Date:   Mon Mar 10 11:57:18 2014 -0400

    More safe buffer

commit 8a89dd3c2b4543475cd0263af0f7e5eeebc12041
Author: Daniel Pehrson <dpehrson@qurve.com>
Date:   Mon Mar 10 11:52:41 2014 -0400

    Test using html_safe
Bump version to 0.7.2
Switch iframe tag to be an explicit content tag
Merge branch 'iframe-tag-fix'
Bump version to 0.7.3
Merge branch 'master' into html-safe