Made the skype and twitter username clickable

* I was not able to link the linkedin username,
  since linkedin does not provide predictable URLS

* The skype url will start skype, and asks if you want to
  call the particular user.

* The Twitter link will just go to the twitter profile
  of the given user
Merge pull request #6012 from jvanbaarsen/social_clickable

Made the skype and twitter username clickable