This fixes a bug where the output would include commas (if editing an existing tagged item). Because the TagField only accepts space-separated single-word tags, the pre-populated comma-delimited value would fail to validate. Thus, the form could not be submitted without manually removing all of the commas. The field's output will now be a simple space-separated list.
This is done so that no special path considerations are needed to import the example app (now found at mediaman.tests.exampleapp), making it much easier to run the tests within the context of a project.