Rewrite patch with pyquery for robustness

Not all HTML can be parsed with a strict XML parser. Some
Sphinx extensions insert HTML from sources outside of the
local author's control (sphinxcontrib-embedly, for example).
In order to support RSS feeds with valid links and the
embedded content from these extensions, use a more forgiving
HTML parser when patching the links.

Change-Id: I045e338289b63832315210b31a7188d5c6ab6570