Links tutorials

[purva-thakre]

As discussed in #33, links to tutorials are added in documentation and readme.md.

For the moment, haven't changed the anchor as requested in above issue since Boxi had a PR for it.

[nathanshammah]

Thanks @purva-thakre. It looks good.

Actually, the other day, I was really looking for this. It would be great to also add an item to the menu bar on the left, for easy access. This can lead to a short .rst page that contains a link to the qutip docs. What do you think?

[purva-thakre]

@nathanshammah I like adding the idea for a new rst page. Let me know what information you would prefer to be added to this. Right now, I moved the line in in the introduction page to tutorials page.

[nathanshammah]

Thanks, looks good to me!

[BoxiLi]

I was wondering, maybe it looks better if the tutorial is added after the user guide? The user guide first introduces necessary concepts, and the tutorials provide hands-on code examples.

[nathanshammah]

Looks good, Purva, and thanks for the additional review, Boxi.