Add fluent setters, that can be used for chaining setters, like in modern Rust

[GamePad64]

Useful for configuration structs.

Closes #77

[Hoverbear]

Appreciate your work, but please understand I don't think this will merge any time soon, if ever. I already think the crate does too much, in the wrong way.

Perhaps you'd be better off making this a separate crate. :)

[kkolyan]

@GamePad64 could you please clarify what do you mean "like in modern Rust"? are there some relevant out-of-the box features?

[GamePad64]

@GamePad64 could you please clarify what do you mean "like in modern Rust"? are there some relevant out-of-the box features?

I don't know about these features in Rust itself, but builder pattern is quite popular in Rust. OpenOptions is a good example for this.