(close #67) Add :mount to Clack.Builder.

Example:
  (builder
    (:mount "/admin" *admin*)
    (:mount "/wiki" *wiki*)
    *default-app*)
v1.0.1
Fix binding of *standard-output* & *error-output* in Clack.Handler.Hunchentoot.
Fix bindings of *standard-output* & *error-output* in Clack.Handler.Toot.
Sleep a little bit after starting & stopping a server.