Rename Filter::Common -> Filter::Misc. Change policy about exporting.
Add BusyBird::Filter. Write POD.
Modules for tests are now under testlib::* instead of BusyBird::Test::*. This is safer and more explicit.
Remove testlib::Input_Twitter because it's no longer used.
Implement Filter.pm. Pass the tests.
Filter, Timeline: improve POD about filters. Specification of filters are described in Timeline. In Filter, it only describes that it provides filters.
Filter::Twitter: revise API spec and POD. Now it has both transformations and filters.
Refector Test::StatusStorage's export tweaks into Util::export_ok_all_tags.
Filter::Twitter: re-implement filter_twitter_* and trans_twitter_* functions. Pass the basic tests.
t/Filter_Twitter.t: now both trans* and filter* functions are tested.