Using users/lookup twitter API

- Lookup users in batches of 100, according to users/lookup API
  call. Using *Mining the Social Web* as a guide for how to
  use the twitter API.
- Trouble using the built-in Cliff table writer since the
  output is in unicode. Instead I write my own CSV file. This
  should be reported as a Cliff bug.
Rename list command to summary
Refactor twitter and wiki reader functions into separate modules