Export debounce and debounceWith (#29)

Yep, more negligence on my part. This commit adds `debounce` and
`debounceWith` to the exports within the `FRP.Event.Time` module.

Author: Tom Harding

src/FRP/Event/Time.purs

@@ -2,6 +2,8 @@ module FRP.Event.Time
   ( interval
   , animationFrame
   , withTime
+  , debounce
+  , debounceWith
   ) where
 
 import Data.Maybe (Maybe, maybe)