disallow deletion of ideas that have been on the board for > 5s

[vanderhoop]

As a retrospective participant who believes that publicly available ideas should not be sneakily removed,
I do not want participants to be able to delete ideas that other participants have had the ability to read and take in,
So that ideas that others have submitted for discussion don't disappear under our feet.

Pre-Reqs:

• completion of disallow deletion of OTHER users ideas #39

Acceptance Criteria:

• after a user's idea has been on the board for 5 seconds, the 'x' button beside that idea disappears.

[vanderhoop]

closing, as i've updated #35 with this criteria