Partially fix #43 by adding ability to clear both kinds of handlers.

src/re_frame/core.cljs

@@ -12,9 +12,12 @@
 (def dispatch-sync    router/dispatch-sync)
 
 (def register-sub        subs/register)
+(def clear-sub-handlers! subs/clear-handlers!)
 (def subscribe           subs/subscribe)
 
 
+(def clear-event-handlers!  handlers/clear-handlers!)
+
 
 (def pure        middleware/pure)
 (def debug       middleware/debug)

src/re_frame/handlers.cljs

@@ -33,6 +33,12 @@
   (get @id->fn event-id))
 
 
+(defn clear-handlers!
+  "Unregister all event handlers"
+  []
+  (reset! id->fn {}))
+
+
 (defn register-base
   "register a handler for an event.
   This is low level and it is expected that \"re-frame.core/register-handler\" would

src/re_frame/subs.cljs

@@ -9,6 +9,12 @@
 (def ^:private key->fn (atom {}))
 
 
+(defn clear-handlers!
+  "Unregister all subscription handlers"
+  []
+  (reset! key->fn {}))
+
+
 (defn register
   "register a hander function for an id"
   [key-v handler-fn]