Avoid corrupt characters in numbered govspeak titles

For some reason assigning directly to inner_html generated a fragment with
incorrect character encoding, if the title contained UTF-8 characters,
or if it contained a single quote character which gets automatically
converted to a curly quote by kramdown.

https://www.pivotaltracker.com/story/show/46976801
Fix test failure on jenkins

Passed locally on my machine (and VM). On jenkins got:

NoMethodError: undefined method `assert_include' for