BusyBird: write "TECHNOLOGIES USED" section.
Filter, Filter::Twitter: improve POD.
Flow: POD: callback argument should not be expanded like "method($callback->($cb_arg))". This is confusing.
Write "method($callback)" and write "$callback->($cb_arg)" in description of the method.
Input::Generator: POD improvement.
Log: now bblog() is exported only by request. Automatic export should be avoided in most cases.
Main: improve POD. add tests for examlpe codes.