add pagination support

[KaulSe]

A different approach than #8. I didn't want to break the return types of the BinaryEdge client, so I decided to add another class that is only responsible for pagination and returns the appropriate return type (Iterator).

[KaulSe]

I wonder if the formatting is good... I played around with autopep8...

[KaulSe]

Any chance of getting this merged :)?

[Te-k]

Hey, thanks! I am not a big fan of having a separated object for pagination. I'll look into it this week-end and test some different code organization.