Notebook updates

[jatinkhilnani]

Following modifications required.

1. librosa.feature.chroma no longer available in latest version and now has three different methods
2. Would be good to mention (or add code cell) mentioning that librosa.display needs to be imported separately (from librosa import display)
3. Also, should the following comment be removed/modified 'Note: major overhaul coming in 0.5'