Do not download the same tweet twice which could slowly waste API calls and bandwidth
remove trailing whitespace
Merge pull request #114 from az0/master

archiver downloads duplicate tweets

The log to the screen shows the downloaded tweets come in sizes 200,199,199.  Example;

    Archiving nprnews tweets in ./nprnews
    Browsing nprnews statuses, new tweets: 200
    Browsing nprnews statuses, new tweets: 199
    Browsing nprnews statuses, new tweets: 199

So I compared the tweet ID keys and found duplicate tweets.