Fix comparison of Twitter::NullObject with Time failed
Fix comparison of Twitter::NullObject with Time failed

Closes #130.

zenspider/t,chastell/t,l371559739/t,freebsdgirl/t,sjfloat/t,zenspider/t,l371559739/t,tjschuck/t,l371559739/t,chastell/t,cyrixhero/t,zenspider/t,zazens/t,cyrixhero/t,tucobenedicto/t,zazens/t,cyrixhero/t,tjschuck/t,sideci-sample/sideci-sample-t,freebsdgirl/t,sferik/t,sjfloat/t,sjfloat/t,zazens/t,sferik/t,chastell/t,tucobenedicto/t,sideci-sample/sideci-sample-t,tucobenedicto/t