Suppress unit test coverage checks in demo code.

Having coveralls complain about uncovered functest / demo code is not helpful.
Silence Python 2.6 deprecation of exception.message.
Merge pull request #227 from tseaver/silence_py26_deprecation_for_exception_message

Silence Python 2.6 deprecation of exception.message.
Merge pull request #226 from tseaver/coverage-ignore_demo_modules

Suppress unit test coverage checks in demo code.