The HTML data in Atom is escaped because the data needs to put as a
string to an XML file. If we are accessing it by reading the string
value, then it is already unescaped, as opposed to getting the raw
XML data.
XHTML data don't need to be unescaped either since the elements are
already encoded as is in tree. :)
Closes#198
The Atom spec says that any title marked with a type of "xhtml" should be
contained in a div element[1] so we need to use the full XML text when
extracting the text.
[1] https://www.rfc-editor.org/rfc/rfc4287#section-3.1
