Update class

+ Renamed $website to $url in `request`
+ Added `CURLOPT_SSL_VERIFYPEER = false` option to curl request
+ Closed curl session before returning (code after return is never
executed)
+ Added array for easy maintenance of signin errors
+ `is_premium` return now boolean
+ `get_skin` return now the skin url
+ removed duplicate code in `render_skin` and user early return to
simplify code
+ removed `?>` end tag, [see
doc](http://php.net/manual/en/language.basic-syntax.phptags.php)
Removed unavailable links

+ Bumped version number
+ changed private to protected (easier to create class extending from
this one)
`login` and `account` functions don't exist...
Updated readme to fit with the current code...

and some other stuffs on the readme such as formatting, cutting long
lines...
Update `account` documentation
Merge pull request #1 from bendem/master

Update class