Alarm.add() should fail if associated data is too big (Closes #2)

Add step to Alarm.add() to fail and set error to "QuotaExceededError"
if the "data" argument exceed an implementation-dependent limit.
Fix 'to to' typo
Merge pull request #20 from cdumez/quotaExceeded

Alarm.add() should fail if associated data is too big (Closes #2)
Remove AlarmRequest interface and use DOM Future instead (closes #23)