Unit test and Travis CI plumbing

[firnsy]

Implement the necessary file layout with a number of real case unit tests.

Unit tests should be nested within a test directory and follow the same directory structure to that which they are testing. For example tests for canvas/package.py would appear in directory test/canvas/test_package.py .

The initial unit tests should also be configured such that the Travis CI service can be used for continuous integration checks.