deprecate midje support and move midje to scope provided

[dchelimsky]

Problem

Within Nubank, we've standardized on clojure.test and deprecated the use of midje. Users who don't rely on midje support incur a transitive dependency on midje anyway.

Solution

• annotate the matcher-combinators.midje namespace and its functions as deprecated
• move midje dependency to :scope "provided"

Rationale

We don't intend to maintain midje support within this library any longer. We have no plan to remove the matcher-combinators.midje namespace outright, so those who depend on it will continue to work as before as long as you maintain an explicit dependency on it.