class definition: close method and class documentation.

class.rkt

@@ -20,6 +20,9 @@
     (define/public (handle)
       ksh)
 
+    (define/public (close)
+      (ks-close ksh))
+
     (define/public (set! key val)
       (ks-set! ksh key val)
       this)

scrbl/class.scrbl

@@ -22,6 +22,11 @@ Opens or creates a keystore using @racket[file]. The meaning of
 @racket[file] is the same as for @racket[ks-open].
 }
 
+@defmethod[(close) boolean?]{
+
+Closes the keystore connection.
+}
+
 @defmethod[(handle) keystore?]{
 
 Returns the underlying keystore handle.