Allow setting bpm and add stutter

[reckoner165]

• Adds bpm() to set the tempo in real time. Checks a couple of boxes off in #7
• Adds a stutter param to aaroha, avaroha and play_notes methods. This stutters each note by the given integer constant
• Updates soundmodular package version to 1.0.1 (includes a method to play silence)

cc @amoghpj