The `size` parameter is optional, defaulting to full size. Note that the
original image's aspect ratio is always preserved, even if this means
-making the image smaller than the specified size.
+making the image smaller than the specified size. You can also specify only
+the width or the height, and the other value will be calculated based on
+it: "200x", "x200".
You can also pass `alt`, `title`, `class` and `id` parameters. These are
passed through unchanged to the html img tag. If you include a `caption`