Util: fix typo.
t/StatusStorage_SQLite: refactor the test into a subroutine (so that we will be able to do 'memory' test)
StatusStorage::SQLite: modify POD and test. ":memory:" should be supported.
StatusStorage::SQLite: bug fix: ack_statuses(), delete_statuses(): the transaction was not properly terminated if the specified timeline does not exists (maybe guard-based transaction management comes in handy in this situation).
StatusStorage::SQLite: add support for ':memory:' storage.
In many tests scripts, use StatusStorage::SQLite->new(path => ':memory:') instead of StatusStorage::Memory, because SS::SQLite is more worthy to be tested.
StatusStorage::SQLite: avoid autovivification of $status->{busybird} when put_statuses(). this is not a serious bug, but should be avoided if it's easy.
StatusStorage::Memory: mention StatusStorage::SQLite in POD.