Modify s/defn to include arglists metadata

 * `process-fn-arity` modified to capture the arglist as passed to the
   function (including the unexpanded schema definition).

 * `process-fn` updated to combine the arglists for each function arity.

 * `defn` modified to pass the attr-map directly to clojure.core/defn,
 rather than as meta-data on the name (slight simplification)

 * `defn` modified to include the arglists in the attr-map
Include arglists in simple-validated-defn-test

Added an extra clause to the simple-validated-defn-test to
ensure that the arglists are passed through as expected.
Update changelog version to 0.1.5
Remove accidentally committed lines from core_test.cljx
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.
Merge pull request #23 from danielneal/feature/include-arglists

Feature/include arglists