Fix spelling mistake in kobo usage

lib/Library.php

@@ -271,6 +271,9 @@ class Library{
 		}
 
 		// Now store various collections
+		apcu_delete('collections');
+		apcu_store('collections', $collections);
+
 		apcu_delete(new APCUIterator('/^collection-/'));
 		foreach($collections as $collection => $sortItems){
 			// Sort the array by the ebook's ordinal in the collection. We use this custom sort function

www/help/how-to-use-our-ebooks.php

@@ -65,7 +65,7 @@ require_once('Core.php');
 				</li>
 				<li id="kobo">
 					<h3>Kobo eInk Devices</h3>
-					<h4>If you’ve download a kepub file</h4>
+					<h4>If you’ve downloaded a kepub file</h4>
 					<p><strong>Important:</strong> <em>Don’t use Calibre to transfer the kepub file!</em> Calibre will apply its own conversion <em>on top of</em> our own conversion, making for strange results.</p>
 					<ol>
 						<li>