Replace whitespaces by "%20" in urls on redirects and .connect(String)

The two new Unittests show that there are problems if the url contains decoded whitespaces " ".
Like: "http://try.jsoup.org/#with whitespaces"
Proposed Fix: The `encodeUrl(String url)` should replace " " by "%20".

On redirects the user doesn't have any chance to handle this, so Jsoup should do it.

Related issues:
- http://stackoverflow.com/questions/18292919/giving-an-url-that-redirected-is-a-url-with-spaces-to-jsoup-leads-to-an-error
- https://github.com/jhy/jsoup/issues/114