Major Description
Currently Graph API is such that when a vertex doesn't receive any messages, compute() is not called upon it.
One way to change it is let the user decide when the algorithm has to stop.
For this we need to add a voteToHalt() function with each vertex.
And maintain a state variable with each vertex. A vertex which has votedToHalt() doesn't send messages in the next superstep. However if it receives any message, its voteToHalt() ends and it is again eligible to send messages.
When all vertices have votedToHalt() algorithm should end.