Implement sing module for bobbit-0.2.x

[pbui]

@camicarballo Created a sing module for bobbit-0.1.x: https://github.com/pbui/bobbit/blob/bobbit-0.1.x/modules/sing.py

Unfortunately it did not work due to the web service blocking the VPS for bobbit. Moreover, it was not ported to bobbit-0.2.x. I would like for someone to implement this functionality:

<- !sing [song title]
-> Random lyric from song