Improve PriorityQueue to use the exact heap algorithm

[samchon]

Until now, PriorityQueue class has used TreeMultiSet as source container. The heap algorithm has been implemented exactly and it also passes the test automation. In such reason, I think it's good time to improve the PriorityQueue class.

• Related issue: Poplar heap is probably not what you want #23

namespace std
{
    export class ProrityQueue<T>
    {
        private source_: TreeMultiSet<T>;

        public top(): T
        {
            return this.source_.end().prev().value;
        }

        public pop(): void
        {
            this.source_.erase(this.source_.end().prev());
        }
        public push(val: T): void
        {
            this.source_.insert(val);
        }
    }
}

From now on, the PriorityQueue class would utilize Vector object and heap algorithm as its source container and arrange method, like below:

namespace std
{
    export class ProrityQueue<T>
    {
        private source_: Vector<T>;
        private comp_: (x: T, y: T) => boolean;

        public top(): T
        {
            return this.source_.front();
        }

        public pop(): void
        {
            pop_heap(this.source_.begin(), this.source_.end(), this.comp_);
            this.source_.pop_back();
        }

        public push(val: T): void
        {
            this.source_.push_back(val);
            push_heap(this.source_.begin(), this.source_.end(), this.comp_);
        }
    }
}