Change LinkedIn sharing URL to secure URL

LinkedIn supports https throughout their site and users should be sent
to https links when possible. This commit changes the Share_LinkedIn
class to use https for the sharing link used in the process_request()
method.
Reverting some unintentional whitespace changes
Using $this->http() to make http usage consistent

Switching from a hard coded https in the LinkedIn class to using
the http() method to make the prefix usage consistent across the
methods and classes.
Merge pull request #973 from enkrates/use-ssl-link-to-linkedin-share

Use ssl link to LinkedIn share