Users can connect to and collect data from Twitter

* Add a sample .env file
* Users can connect to Twitter
* Twitter data can be collected using the `rake` task `collect_twitter_data`
* Remove `pow`-related setup from `bin/setup` since we're not using it
* Up `unicorn` request timeout to `25`. The previous timeout could cause
* problems when connecting to Twitter.
* Don't load factories twice in the `development_seeds` `rake` task. This
* would cause errors when run.

https://trello.com/c/nXLz7lTf