use python twitter tools to connect to twitter api

Changes `TwitterTaskHandler` to use the [Python Twitter Tools](https://github.com/sixohsix/twitter) module to connect to twitter api with application specific oauth credentials. I have the credentials in a text file (not under source control) that I can share via email, or you could just create your own credentials with twitter and save them in a file named `twitter_api.cfg` with the format:

    Consumer key: key-goes-here
    Consumer secret: secret-goes-here
    Access token: access-token-here
    Access token secret: access-token-secret-here

This commit will not work without the credentials file. We may want to change the way the credentials or accessed, but it should be fairly easy to do so.

This commit includes a complete copy of the PTT source, which I had to modify slightly to exclude a reference to a C module (_ssl) that Google App Engine does not support. So unless we find a work around, we'll have to keep it in the repo. 

I tested locally, and everything worked just fine. Please let me know if there is anything I need to change, especially where my code is not 'pythonic'. I tried to stick to the conventions already shown, but I may have missed something. Thanks!