[wiki] Create wiki page about Social Metrics tracked by Komito

[vpodk]

Screenshot of Social Plugins from Google Analytics:

Logged in users

• pageview - This is page views by users logged in to social networks. Supported: Facebook, Google+, Twitter.

Social interaction

• Twitter events: favorite, follow, retweet, tweet and intent-tweet;
• Facebook events: like, unlike and message;
• LinkedIn events: share and follow.