Rails now handles html_safe when using string ranges
to replace text.

We need to mark the replacement text as HTML-safe so that it
doesn't get escaped when it gets inserted into the HTML-safe
string.

Example:

string = "<p>Hello</p>".html_safe
string[3..4] = "<b>He</b>"

"<p>&lt;b&gt;He&lt;/b&gt;llo</p>"

Correct way:

string = "<p>Hello</p>".html_safe
string[3..4] = "<b>He</b>".html_safe

"<p><b>He</b>llo</p>"