Adds support for tracking indexes

[kieraneglin]

It's useful for me to know what indexes exist on my tables for the purpose of troubleshooting performance issues, so I added it to this project! You can see it in use here

There's a new flag (--skip-index) if you want to ignore indexes which effectively keeps the current behaviour.

Default output:

With --skip-index:

[inukshuk]

Thanks!