Use textwrap.shorten for tweets that are too long

[Brian Mitchell]

textwrap.shorten would be a great function to auto-truncate a tweet that is too long.

This wasn't added to the standard library until python 3.4, so this will require a breaking change.

[Brian Mitchell]

This change would belong somewhere around https://github.com/BrianMitchL/weatherBot/blob/development/weatherBot.py#L231

[A. Fox]

See PR WTFox#1

I noted a few things in the PR body that might be of interest.