First of all this is not a complete answer, a few suggestions only. I don't think you can find a tutorial to create a library for twitter. Twitter also not giving any SDK only they documented the rest apis and their use here. They are using OAuth1.0 for user authentication. So you need to authenticate the user to access these api.
For authentication:
- Authentication through web view
- Reverse auth
Its better to check an open source implementation and make yourself. FHSTwitterEngine is one of them that you can refer. It is lacking reverse auth, you may want to add.