Added Imagick to docs (#211)

docs/Settings.md

@@ -44,4 +44,10 @@ A typical part of a MySQL statement. This string will be appended to mostly ever
 
 This key is required to use the Dropbox import feature from your server. Lychee will ask you for this key, the first time you try to use the import. You can get your personal drop-ins app key from [their website](https://www.dropbox.com/developers/apps/create).
 
-	dropboxKey = Your personal App Key
+	dropboxKey = Your personal App Key
+	
+#### Imagick
+
+	imagick = [0|1]
+	
+If `1`, Lychee will use Imagick when available. Disable [Imagick](http://www.imagemagick.org) if you have problems or if you are using an outdated version. Lychee will use [GD](http://php.net/manual/en/book.image.php) when Imagick is disabled or not available.