Allow for literal specification of values in contracts

[gsinclair]

The contract String => Any requires the argument to be a string object.

The contract 5 => Any requires the argument to be the actual value 5.

So how do I specify that the argument should be the actual value String? This is how it could be specified: Literally[String] => Any.

[waterlink]

@gsinclair Hi, thanks for opening this issue. This sounds like a valid builtin contract. Are you up to making a PR ?

[egonSchiele]

You should be able to use the Eq class for this.

[waterlink]

I see, I have forgot about it. And apparently it is not documented in TUTORIAL.md here: https://github.com/egonSchiele/contracts.ruby/blob/master/TUTORIAL.md#built-in-contracts

[gsinclair]

Heh... Eq is a much better name, too. I'll do a PR with the documentation.

[jeremyf]

@gsinclair Can this issue be closed?

[gsinclair]

Yes. I didn't realise it was for me to do so. Closing.