fix for attributes containing quotes like ng-include="'val'"

When using a library such as AngularJS it is possible that tag values will contain single quotes like this:
<div data-ng-include="'path/to/template'"></div>
to indicate a String value rather than a variable value.
The attr regex matches the first ' as the end of the attribute rather than the second ".  This commit updates the regex to match the closing quote delimiter to the opening delimiter