Twitter support!

This allows to submit your twitter profile to submissions and interests (82778f3)

We also got a tweet-about button after the creation of a talk/interest. It is cookie based like votes. (fc78203
)

this needs #34 and #33 (hapi updates) and #37 (XSS, filtering) merged before, they are included in this optimistic branch
Not sure if we need to check for all the values (title etc) again in this test or if just checking for the twitter handle is sufficient.