Fix title attribute values

* Some values of title attributes had hardcoded references to one of
  the compared versions of text. They now refer to these versions using
  the titles as set in the renderers options.
* Values can contain character sequences that break the HTML output of
  the renderer. The characters are now converted to HTML entities.

lib/jblond/Diff/Renderer/Html/Merged.php

@@ -186,7 +186,7 @@ public function generateLinesDelete(array $changes): string
     {
         $this->lineOffset -= count($changes['base']['lines']);
 
-        $title = "Lines deleted at {$this->options['title2']}:\n";
+        $title = "Lines of {$this->options['title1']} deleted at {$this->options['title2']}:\n";
 
         foreach ($changes['base']['lines'] as $lineNo => $line) {
             $fromLine = $changes['base']['offset'] + $lineNo + 1;
@@ -197,7 +197,7 @@ public function generateLinesDelete(array $changes): string
 TEXT;
         }
 
-        $this->lastDeleted = $title;
+        $this->lastDeleted = htmlentities($title);
 
         return '';
     }