Fixing annotation on the outputDirectory property.  From history, it appears the 'expression' argument name was accidentally changed while updating source formatting.
Tests are failing to execute because both Maven 3.0.4 and Maven 2.x are in the dependency tree.  Updating dependencies to eliminate Maven 2.x from the dependency tree.
An integration test is required to correctly validate this issue.  We need to ensure the test project's build output is on the classpath when using the plugin in a traditional project build.  Simply adding a new test to the current unit testing framework does not correctly mimic the scenario.  I'm adding the capability to execute integration tests using the  maven-invoker plugin and creating an integration test for this issue.  The test currently fails as expected.