Data update

[dmil]

Data update from researchers at Clemson University (including @patrick-lee-warren)

Major Changes:

• removes accounts that were accidentally included (closes #16)
• adds alt_external_id, tweet_id, and article_url (closes #8)
• adds fields that follow http(s)://t.co/ links to their first redirect if they exist in a tweet
• fixes some issues about how ids are displayed (closes #4)
• fixes double encoding issue (closes #5)
• drops some duplicate observations
• updates README to reflect changes

closes #26

[EvanCarroll]

You say major changes, but most of those changes are already commited. We can't see the data-update either with the browser. Could you tell us what you did? Have you seen my PR here #29

What I did is pull down the data files from @patrick-lee-warren and self-host them within PostgreSQL. I also created a script to dump them (so we don't keep committing the whole repo). I also pruned the duplicates.