added page method to retrieve full url [like: /wiki/#{HTML_Escaped_Page_...

Hi!
retrieve a Page URL using `Page#fullurl` seems to not work anymore (always retrieves `nil`).
I changed it to correctly retrieve the Page URL from Wikipedia, using:
- configuration to generate the correct URL
- URI encode the page title
- appending curid

`#{protocol}://#{domain}/wiki/#{HTML_Escaped_Page_Title}?curid=#{curid}`

Note: Page title could be anything as soon as we provide a curid.