Import tweets from user timeline instead of search

[tommarmstrong]

Importing tweets currently uses the Search API endpoint which has some limitations:

• Not guaranteed to be complete (some users / tweets may be missing)
• Can only search through the last 7 days of tweets

It could be better to implement the User Timeline endpoint which reads from a users timeline instead of performing a search. This has the advantage of being complete and can return results over a larger period (up to 3200 tweets of history per timeline)