Change format for the hour time span, to prevent clobbering up with minutes

For example, if an event `test` happens at 13:49, minuteman records it to these keys:

`minuteman_test_2014-05-22 13:49` (from the minute time span)
`minuteman_test_2014-05-22 13:00` (from the hour time span)

Which can be mistaken for the event occurring twice, once at 13:49 and once at 13:00.

By changing the format for the hour timestamp, it is no longer possible to confuse these two, as the same event is recorded so:

`minuteman_test_2014-05-22 13:49` (from the minute time span)
`minuteman_test_2014-05-22 13` (from the hour time span)

If an event should happen at 13:00, it will be recorded as:

`minuteman_test_2014-05-22 13:00` (from the minute time span)
`minuteman_test_2014-05-22 13` (from the hour time span)

Does this make sense?