fixing missing titles with s/cat and s/merge

[wandersoncferreira]

Hi! This PR attempt to solve #197 however there are some points I wanted to make clear.

1. I might be obvious, but the :title will be show up only if your s/merge or s/cat is defined because

(st/spec-name (s/merge ::one ::two)) ;; => nil

Therefore, only if you use something like:

(s/def ::merged (s/merge ::one ::two))
(st/spec-name ::merged) ;; => full-qualified/merged

2. This PR depends on another open PR allow option to toggle title inference from specs #221 which will enable the title added by this PR to be customizable by the end user. However, I am not sure how to deal with this dependency here. What I end up doing was to leave this PR completely independent from the other one and once both of them is merged I will open a new one finishing the work. I did this because the other PR is more opiniated and if we have implementations change it could affect this one too.

Thks

[coveralls]

Coverage increased (+0.009%) to 97.89% when pulling 800e354 on wandersoncferreira:fix/missing-titles into d043282 on metosin:master.

[ikitommi]

Thanks again :)