"*Queue" is a priority queue of "*Candidate".
"NewQueue" creates an empty queue of "*Candidate".
"(*Queue).Len" return the size of the queue.
Fix: "(*Queue).Pop" returns the candidate which has the highest priority in the queue.
TODO: Sort the nodes of "(*Predictor).ngramTrie" with their scores.
Fix: Pass required arguments and returns the appropriate number of values.
Fix: Pop candidate correctly.
Merge branch 'feature/generate-candidates'