Log Message:
Changes 0.311:
* require the correct version of Getopt::Long::Descriptive

Changes 0.310:
* classes are now loaded with Class::Load, which should avoid bugs
  where classes are not succesfully loaded by program execution
  continues anyway
* more checking is now done to ensure that plugins are members of the
  correct base class

Changes 0.309:
* skip a failing test on perl 5.8.x

Changes 0.308:
* When App::Cmd::Setup tries to load MyApp::Command, and it exists but
  will not compile, the exception will now propagate.  Previously, it
  failed silently and App::Cmd::Command was used instead.