Exercise 31: Music, math, and email queries

1.	"Play {song_title}", "Play the song {song_title}", and "Play the song {song_title} at {number} percent volume". All of a user's iTunes songs should work. Implement "Pause", "Pause the song", "Resume", "Resume the song".

2.	"What is X * Y?", "What is X + Y?". For now, only implement math for numbers between 1 and 19 since command and control voice recognition won't recognize larger numbers by default.

3.	"Ask Meredith when she'll be home". Send a pre-formatted email to Meredith asking her when she'll be home, and use a return email address of "grace.bigham@gmail.com". Check the Gmail account once every minute for a reply. If the email is replied to, speak the response.