Make exception handling compatible with Python 2.5

This is a short term fix suggested by Peter Chater on the mailing list that will allow the code to be used with Python 2.5 - a better solution will be needed when we merge in the Python 3.0 support
Fix function documentation for PostDirectMessage
Update GetFollowerIDs with total_count to limit API calls

Updated GetFollowerIDs() with a total_count parameter which will limit
the total amount of retrieved FollowerIDs to avoid getting rate limited
by twitter. Also made it clear in the parameter documentation that
setting 'count' to a small value might get you rate limited rather
quickly.