Randomized queue. A randomized queue is similar to a stack or queue,
except that the item removed is chosen uniformly at random from items in
the data structure. Create a generic data type RandomizedQueue that
implements the following API:

Subset client. Write a client program Subset.java that takes a
command-line integer k; reads in a sequence of N strings from standard
input using StdIn.readString(); and prints out exactly k of them,
uniformly at random. Each item from the sequence can be printed out at
most once. You may assume that k ≥ 0 and no greater than the number of
string N on standard input.