BLK-179 Rest polling only resets the recent posts for the current query

Signed-off-by: Oren Leiman <oleiman@neutral.io>
BLK-179 Avoids repeating work in RESTPolling._discard_duplicate_posts

Signed-off-by: Oren Leiman <oleiman@neutral.io>
Merge pull request #18 from nio-blocks/bug/overzealous_reset

BLK-179 Rest polling only resets the recent posts for the current query