Encode URL

The method **cl_image_tag** doesn't appear to return a fully encoded URL.

Take the following filename as an example:

```
Folder's/logo.jpg
```

In order to avoid any HTML errors I would have expected the following:

```
Folder%27s%2Flogo.jpg
```

However, the following is returned and as such breaks the img element:

```
Folder's/logo.jpg
```