Update the twitter package version requirements. Fixes #133.

A change to Twitter's public API broke libraries supporting the Streaming
API, including the twitter package used with MTSW. Patches to the twitter
library subsequently fixed the breakage.

Pre-existing users of the virtual machine should simply upgrade their
twitter package with pip via "pip install twitter==1.12.1"
Enhancements to Exs. 6-3 & 6-13 for Google Takeout

Enhanced Example 6-3 so that it "just works" with Google Takeout data
continaing Unicode where previously an exception was being raised
due to a string being mistakenly decoded twice.

Enhanced Example 6-13 so that email addresses that serve as the basis of
the query are substrings in the From field instead of exact matches,
making it easier to query for known addresses

See also these gists for enhancements with debugging data that may also
be useful.

* https://gist.github.com/ptwobrussell/8791064
* https://gist.github.com/ptwobrussell/8875470