Added publishing functionality to Pubsubhubbub

Added the functionality of sending the alert to Pubsubhubbub.

Right now we have all the valid info only about pubsubhubbub . Will add a broker table later as and when more brokers are available.
Recall Dominic said: "Always use self.request or r inside an S3Method, not current.request".  So, you have r already as an argument -- getting it out of self is actually extra time.