Fix input/textarea debouncing logic

[wwwillchen]

Right now if a user types in an input/textarea component and then quickly does another action (e.g. click a button), then there's a race condition where the button click action may happen before the input debounce completes which creates an unintuitive behavior.

Short-term fix: Adjust it down to 150ms (currently 300ms)

Long-term fix: Have some mechanism for queueing user events in the Channel so that the input is guaranteed to be before any other event (in the above example sequence).

[wwwillchen]

Removing from v0.5 milestone because the short-term fix is in and the long-term fix is a little bit unclear ATM.