Fix the test classpath.

Tests should include everything on the main classpath, otherwise
you get DMDirc classes extending 3rd party classes, and everything
starts to break when the base classes go bye-bye.

Change-Id: I7579d833bd31ccf12a93da8c3ea8fff3c2a0eff7
Reviewed-on: http://gerrit.dmdirc.com/2771
Automatic-Compile: DMDirc Build Manager
Reviewed-by: Greg Holmes <greg@dmdirc.com>