Improve first-touch demo

[brohrer]

For a user's first experience with becca the workflow is

pip install becca
python3
>>> import becca_test.test as test
>>> test.suite()

Which runs the test suite.

This could be improved in several ways:

1. Have a more interesting world run, such as a simulated robot.
2. Have a demo() method available through the becca package, rather than having to import becca_test
3. Have more verbose console feedback about what's going on, to give the user a sense of what's happening behind the scenes.
4. Have any output images saved to an easy-to-reach directory, perhaps the pwd() or pwd()/demo.
5. Have the world create its own static visualizations to illustrate what is happening.
6. [Gold medal, over-the-top] Have the world serve its own live animation of what is happening.