Added conditional validation example

[igor-alexandrov]

No description provided.

[apotonick]

That's a great addition, thanks @igor-alexandrov - the problem is only, do we actually want to push validation groups or rather high-level rules in dry-v?

Also, I'm contemplating rewriting most parts of the Reform docs. Are you interesting in helping? We could start with discussing structure and examples, and then go for it!?!

[igor-alexandrov]

@apotonick sure I want to help. Also I like the idea of how DRY keeps their documentation: they don't have anything in README and all documentation is on their site: http://dry-rb.org/gems/dry-validation https://github.com/dry-rb/dry-validation. This is easier to maintain and keeps everything in one place.

[igor-alexandrov]

As for me, validation groups are more understandable than high-level rules.