Another bugfix release for the Highlight plugin's tests. Now there is a Travis build that explicitly tests for the absense of recommended modules, which should prevent this in the future.

Full changelog below...

• use fake site for command error tests (#426)
• report stdout/stderr on test failure
• do not test Highlight plugin compile
• only load Devel::Hide during test
• install Devel::Hide during travis build
• add travis build that hides optional dependencies