In a large mixing bowl combine the couscous, boiling water and olive oil. Quickly stir with a fork and cover the bowl with a pot cover or large plate so that the steam stays in the bowl. Let sit for 5 minutes and then fluff with a fork to break up the grains. Let cool to room temperature or place in the refrigerator to chill. While the couscous is chilling, prepare the vegetables. Just before you're ready to serve, combine the couscous with all the chopped ingredients. Toss gently to combine. Add the vinaigrette and toss again. Serve immediately. In a small bowl combine the vinegar with the mustard, salt and pepper. Using a fork, stir until the salt is dissolved and the mustard completely mixed. Add the olive oil and whisk with the fork until it has combined with the vinegar. Add immediately to the salad. If it sits for a while, re-mix it before adding to the salad because if it has separated back into oil and vinegar the couscous grains may absorb it unevenly.