Twitter example uses deprecated 1.0 API

Our example for reading Twitter feeds uses the 1.0 version of the Twitter API. This API has now been deprecated and queries fail with...

{"errors": [{
  "message": "The Twitter REST API v1 is no longer
              active. Please migrate to API v1.1.
              https://dev.twitter.com/docs/api/1.1/overview.",
  "code": 68
}]}

This causes our example to fail with...

atagar@morrigan:~/Desktop/stem$ python twitter_script 
Traceback (most recent call last):
  File "twitter_script", line 39, in <module>
    print "%i. %s" % (index + 1, tweet["created_at"])
TypeError: string indices must be integers

Patches welcome for migrating the example to the 1.1 API!

Trac:
Username: ovnicraft