update_status_with_media call change

Change 'r' to 'rb' mode to ensure filename/pathtofilename parameter (string) passed as media[] argument works
u'' or None instead of None or u'' will fix missing parameter status issue in case of empty tweet and valid photo file(passed as filename/pathtofilename mentioned above)
Merge pull request #10 from ShriramK/master

Improve parameter checking in update_status_with_media and ensure media file is opened in binary mode