Fix http / https protocol requirement.

Trying to fix issue #113

Fix the http / https prefix requirement when adding a bookmark without prefix by :
1 - Constructing URLs for both protocols,
2 - Retrieving both pages titles,
3 - Choosing the one which works, with a systematic preference for https.

I'd be glad to hear from anyone about several things to discuss :
- I have choosed to always test for the original submitted url, the submitted url with http prefix, and the submitted url with https prefix, but I don't know if that is the best way to achieve tests,
- What about the original (s)ftp bookmark support ? Do you think it is worth keeping it ? in such case, wouldn't it be a bit stupid and heavy to always retrieve each possible page to test each protocol ?
- Should users have their bookmark links always enforced to https if the remote server supports https ? I have currently choosed to respect user's input when they specify a protocol : if you input http://github.com, the bookmark will respect your choice and won't switch to https..
- Problem : In case where https has been implemented on the remote server but the website is not properly configured to work with it, it can end-up obtaining "403 Forbidden" bookmarks titles (experiment it by adding "lefigaro.fr" as bookmark).

Great thanks in advance for sharing your thoughts !! :)
Why don't we simply use `else`? Maybe a tiny optimization.