Move changelog notes to 1.4
Add return-type to doc string

The unexpanded form of the schema is prepended to the doc-string.

This means that a function like:

     (s/defn is-this-the-answer? :- (s/maybe String)
        "Returns an affirmative statement if x is the answer to life, the
         universe and everything, otherwise, return nil."
        [x :- Integer]
        (when (= 42 x)
           "Yes, 42 is the answer to life, the universe and everything")

Would return a doc-string as follows:

     schema.macros/is-this-the-answer?
     ([x :- Integer])

     Returns: (s/maybe String)

       Returns an affirmative statement if x is the answer to life, the
       universe and everything, otherwise, return nil.